<p>The correct answer is <strong>(B) be instructed</strong>.</p>
<p>In this sentence, the verb "thinks" is followed by a subordinate clause, "is it imperative that employees ______ regularly." This subordinate clause expresses a demand or necessity. </p><p>According to the grammar rule of subjunctive mood, when expressing a demand or necessity, we use the base form of the verb (in this case, "instruct") after the word "that." However, in English, we use the subjunctive mood by using the bare infinitive form (base form) of the verb after certain verbs such as "demand," "insist," "recommend," "propose," "request," and "suggest." Therefore, the correct form is "be instructed" (the bare infinitive form of "instruct").</p>
<p>Let's analyze the other options:</p>
<p>(A) "instruct" - This option is in the base form of the verb, but it does not follow the subjunctive mood rule that is required in this sentence. Therefore, it is incorrect.</p>
<p>(C) "instruction" - This is a noun form, and it does not fit grammatically in this sentence. Therefore, it is incorrect.</p>
<p>(D) "instructed" - This option is in the past tense form of the verb, and it does not follow the subjunctive mood rule that is required in this sentence. Therefore, it is incorrect.</p>