The correct answer is A, past.
The verb taught is a past tense verb or a past participle. This automatically excludes C, present and D, future.
The choice is now between A and B. To form a past perfect you need the verb "to have" in the past, "had". Because there isn't an auxiliary verb here, it is in the past. It also helps to look at the word "yesterday", which shows us this is a past action but not that far in the past to be called a "past perfect".
