多益閱讀文法 - Present, Past, and Future Perfect Tense

Key Points

The Present Perfect Formula: have/has + past participle
The past participles of regular verbs are usually formed by adding the suffix “-ed” (e. g., “learn” becomes “learned”). The past participles of irregular verbs have numerous endings like “-en,” “-n,” “-ne,” and “-t” (e. g., “kneel” becomes “knelt”).

The present perfect is mainly used in the following situations:
(1) Expressing actions started in the past and continuing in the present
(2) Emphasizing what has been done or happened
(3) Talking about actions that have been repeated many times in the past

Subject + have/has + past participle

over/in/for/during + a past period of time
since + time in the past
since + subject + past tense verb

so far/up to the present time/up to now
lately/recently/these days

The correct answer is (C) has stabilized.

From “over the past month”, we know that this sentence should use the present perfect tense. The present perfect tense is formed with "has/have + past participle." In this case, "has stabilized" fits the context perfectly, indicating that the price of gold became stable in the past and remains so currently.

(A) "is stabilizing" is incorrect because it suggests that the action of stabilizing is happening right now or continuously, which contradicts the past time context mentioned in the sentence ("over the past month").

(B) "will have stabilized" is incorrect as it refers to the future perfect tense, indicating an action will be completed before another action or time in the future. The sentence is discussing a past-to-present situation, not a future one.

(D) "will be stabilizing" is incorrect because it uses the future progressive tense, suggesting an ongoing action that will take place in the future, which again does not fit the context of the sentence.

The correct answer is (B) have been gradually dropping.

The use of "over the past 10 years" indicates a duration from the past until now which further confirms the use of the present perfect continuous tense. The present perfect tense is formed with "has/have + past participle." Hence, "have been gradually dropping" is the correct answer.

(A) "had dropped gradually" is incorrect as it uses the past perfect tense which is used to show that an action was completed at some point in the past before something else happened. This is not fitting in the context of the sentence as it does not indicate that the drop in house prices is a continuing action.

(C) "dropped gradually" uses the simple past tense, which is used to talk about a completed action in a time before now. In this context, it suggests that the action of house prices dropping has been completed, which doesn't fit the context.

(D) "drops gradually" is in the simple present tense, which is used to describe an action that is habitual or usually happens. It does not fit in this context as the sentence talks about a specific period "over the past 10 years", not a general habit or routine.

Past tense

I saw a great movie last week.
Madison ate too much last month.
I arrived in Tokyo 5 minutes ago.
I met Elon Musk last year at a conference.

Present perfect tense

I have seen that movie.
Madison has eaten too much recently.
I have arrived in Tokyo.
I've met Elon Musk before.

have gone to
(Someone went somewhere but hasn't come back yet.)

A: I haven't seen Mike recently. Where is he?
B: He's gone to Miami for a business trip.

have been to
(Someone went somewhere and has come back.)

A: Hi! Mike. How was your trip?
B: It was great. I have been to many cities like Miami and Boston.

Key Points

The Past Perfect Formula: had + past participle
The past participles of regular verbs are usually formed by adding the suffix “-ed” (e. g., “learn” becomes “learned”). The past participles of irregular verbs have numerous endings like “-en,” “-n,” “-ne,” and “-t” (e. g., “kneel” becomes “knelt”).

The past perfect tense is used to indicate a completed action or condition that occurred before another event in the past. It is formed by using 'had' followed by the past participle of a verb.

Past perfect tense often involves two past time points, so if you come across a sentence structure like the one below, it's considered "past perfect".

(1) Subject + had + past partciple + until/before/by the time + subject + past verb
(2) When + subject + past verb, subject + had + past partciple
(3) Subject + past verb + because/since + subject + had + past partciple

The correct answer is (C) had known.

The sentence uses the past perfect tense ("had known") to indicate that the senior managers knew about the financial problems before another event in the past (the news being made public). The past perfect tense is used to show that an action happened before another action in the past. In this case, their knowledge of the financial problems occurred before the news was made public.

(A) “know” is incorrect because it is in the present tense, which doesn't fit with the past context of the sentence.

(B) “have known” is incorrect because it is in the present perfect tense. This tense is used to indicate an action that happened at an unspecified time before now. The sentence, however, specifies a clear time frame (before the news was made public), so the present perfect tense is not appropriate.

(D) “knowing” is incorrect because it is a gerund and doesn't function properly in this sentence. The sentence needs a verb to indicate the managers' past knowledge of the financial problems, not a noun (which is what a gerund is).

The correct answer is (C) had been delayed.

The sentence uses the past perfect tense ("had been delayed") to indicate that the delay of the shipment occurred before another event in the past (the buyers being notified). The past perfect tense is used to show that an action happened before another action in the past.

(A) "being delayed" is incorrect because it is a present participle and does not fit the past context of the sentence. This option would be used if the delay is happening in the present, which contradicts the context of the sentence.

(B) "would be delayed" is incorrect because it uses the future conditional tense, which shows that an event will happen in the future under certain conditions. In this sentence, however, the event (the shipment delay) has already occurred in the past, so the future conditional tense is not suitable.

(D) "have delayed" is incorrect because it is in the present perfect tense. This tense is used to indicate an action that happened at an unspecified time before now. In this sentence, however, a specific event in the past is being referred to (the shipment delay), so the present perfect tense is not appropriate.

Key Points

The Future Perfect Formula: will have + past participle
The past participles of regular verbs are usually formed by adding the suffix “-ed” (e. g., “learn” becomes “learned”). The past participles of irregular verbs have numerous endings like “-en,” “-n,” “-ne,” and “-t” (e. g., “kneel” becomes “knelt”).

The future perfect tense is used to describe an action that will have been completed by a certain point in the future. It's typically used with time expressions such as "by" or "by the time". The structure is "subject + will have + past participle". For example, "By next year, I will have graduated from college." This indicates that the action of graduating will be completed by a specific time in the future, which is next year in this case.

Subject + will have + past participle

by + future time
by the time + future time
by the time/before/when/the next time + subject + present tense verb + future time

Key Points

The Future Perfect Formula: will have + past participle
The past participles of regular verbs are usually formed by adding the suffix “-ed” (e.g., “learn” becomes “learned”). The past participles of irregular verbs have numerous endings like “-en,” “-n,” “-ne,” and “-t” (e.g., “kneel” becomes “knelt”).

The future perfect tense is used to describe an action that will have been completed by a certain point in the future. It's typically used with time expressions such as "by" or "by the time". The structure is "subject + will have + past participle". For example, "By next year, I will have graduated from college." This indicates that the action of graduating will be completed by a specific time in the future, which is next year in this case. 

Subject + will have + past participle

by + future time
by the time + future time
by the time/before/when/the next time + subject + present tense verb + future time

The correct answer is (C) will have been spent.

This is an example of the future perfect tense, which is used to indicate that an action will have been completed at some point in the future. In this case, the action is the spending of $10 million on sustainable technology and research into the impacts of climate change. The future perfect tense is used here because the spending is expected to be completed by next year.

(A) "is spent" is incorrect because it is in the present tense, suggesting that the $10 million is currently being spent, which contradicts the time indicator "by next year".

(B) "will spend" is incorrect because it is in the future simple tense, suggesting that the $10 million will start to be spent at some point in the future, but without any indication of completion.

(D) "will have spent" is incorrect because it is in the future perfect tense, but the passive voice is needed in this context. The money is not the agent doing the spending, but being spent. Therefore, the passive form "will have been spent" should be used.