Select the correct passive form of the given sentence.
The Inspector had already proved the case before the investigation team took charge of it.

A

The investigation team took charge of the case but the Inspector had already proved before it.

B

The case had already proved by the Inspector before the investigation team took charge of it.

C

The case was already proved by the Inspector before the investigation team took charge of it.

D

The case had already been proved by the Inspector before the investigation team took charge of it.