An action in a sentence can be represented in two ways, namely active and passive voice.
The passive voice always uses the past participle form of the main verb irrespective of any tense. Only the auxiliary verbs depend upon the sentence given in the active voice.
The option B is correct as the given sentence is in the active voice and to transform it into passive voice the subject of the given sentence
(He) comes in the place of the object (us) and vice-versa. Also, as the sentence is in the simple present tense, 'are' is used before the past participle form of the main verb (teach).
Options A, C, and D are wrong as the subject is not in its correct place, the sentence is not in the simple past tense, and the given sentence is not in the future tense respectively.
The correct answer is B)We are taught grammar by him.