Andrei prefers that his mentor focus more on trigonometry instead of algebra. The sentence above uses the verb mood in the imperative. subjunctive. conditional. interrogative.

I would definitely go with B because a subjunctive is an realist mood (one that does not refer directly to what is necessarily real) - it is often contrasted with the indicative, which is a realist mood. Subjunctives occur most often, although not exclusively, in subordinate clauses, particularly that-clauses.