Topic: verb (ক্রিয়া),

Best Answer Explained in Below-:

The correct choice for the sentence "The boss prefers that he--- with his clients personally" is option B: "speak." This construction employs the subjunctive mood, which is commonly used in English after verbs expressing desire, preference, or necessity, such as "prefer," "suggest," or "recommend."

In English, when we use the subjunctive mood, the base form of the verb is typically used regardless of the subject. Here, "he" is the subject, and "speak" is the base form of the verb. The subjunctive mood emphasizes that the action (in this case, speaking with clients) is desired or recommended by the boss, rather than an indication that it is currently happening or will definitely happen.

The other options do not fit the context appropriately:
- "speaks" (A) is incorrect because it is not in the subjunctive form.
- "is to speak" (C) implies obligation or future arrangement, which alters the intended meaning.
- "speaking" (D) is a gerund and does not fit the structure of the sentence.

Therefore, "speak" is the correct choice as it accurately conveys the boss's preference in a grammatically and contextually appropriate way.