Question

They had already closed the shop.

Answer 1

$\huge{\mathtt{\purple{A}\green{N}\pink{S}\blue{W}\purple{E}\green{R}\pink{!}\blue{!}}}$

The shop had already been closed by them.

Extra Information :

When changing the voice from active to passive, at first the subject, object, and verb of a sentence must be identified. Then, the tense of the verb must be noted, because to transform the voice from active to passive, the necessary form of the helping verb should be used. It is succeeded by the past participle form of the main verb.

The given sentence is in past perfect tense and we know that the passive voice form in the past perfect tense is made by putting had + been before the past participle form of the main verb.