The answer choices for this type of problem are all or almost all different forms of the same verb. From the context of the sentence stem, you’ll have to decide which form works best in the sentence. Distractors are generally incorrect for one of these reasons:
The architect designed the building.
(active verb)
The building was designed by the architect.
(passive verb)
∇ Sample Item
Before the late eighteenth century, most textiles ________________ at home.
(A) produced
(B) was produced
(C) producing
(D) were produced
Choice (D) is the best answer. (A) can be considered either an active verb in the past tense or a past participle; both are incorrect. An active verb is incorrect because a passive verb is needed; a past participle is incorrect because a past participle cannot serve as a main verb. (B) is incorrect because the plural subject textiles requires a plural verb, were. (C) is incorrect because, by itself, an -ing form can never be a main verb.