<p>If the mechanic had come this morning, the air conditioner <strong>would be</strong> working now.</p>
<p>The correct answer is <strong>(A) would be</strong>.</p>
<p>In this sentence, we are using the second conditional tense to talk about a hypothetical situation. The sentence is in the past unreal conditional form, which is used to talk about something that did not happen in the past. In this case, the mechanic did not come this morning, so we are talking about what would have happened if he had come.</p>
<p>The verb form "would be" is used to express the result or outcome of the hypothetical situation. It indicates that if the mechanic had come, the air conditioner would currently be in a working state.</p>
<p>The other options are not correct:</p>
<p>(B) would have been - This form is used to talk about a hypothetical situation in the past that did not happen. However, in this sentence, we are talking about the present result of the hypothetical situation, so "would have been" is not the correct form.</p>
<p>(C) will have been - This form is used to talk about a future result of a past action. However, in this sentence, we are talking about the present result of a past action, so "will have been" is not the correct form.</p>
<p>(D) will be - This form is used to talk about a future action or state. However, in this sentence, we are talking about the present result of a past action, so "will be" is not the correct form.</p>