Change the following from active to passive: The storm damaged many houses.

Correct — C. The active verb is damaged, simple past.

The simple past passive is was/were + past participle. The new subject, many houses, is plural, so the auxiliary is were.

The doer, the storm, moves into the by-phrase: Many houses were damaged by the storm → option (c).

Why the others are wrong

• (a)
  Many houses are damaged by the storm. — are damaged is the present simple passive, the passive of damages. The active verb is past, and changing the voice never changes the tense.
• (b)
  Many houses had been damaged by the storm. — had been damaged is the past perfect passive, the passive of had damaged. The active sentence has no had, so the tense has shifted.
• (d)
  Many houses have been damaged by the storm. — have been damaged is the present perfect passive, the passive of have damaged. It moves a simple past action into the present perfect.

Changing the voice changes the verb's form, never its tense.

The active object becomes the subject, the active subject moves after by, and be takes the tense of the active verb, followed by the past participle.

damages → is/are damaged
damaged → was/were damaged
has damaged → has/have been damaged
had damaged → had been damaged

Key facts

• Simple past active becomes was/were + past participle in the passive.
• The auxiliary agrees with the new subject: many houses were, one house was.
• In a voice change, be takes the tense of the original active verb.

Common traps

• Choosing have been damaged because the houses may still be damaged now, when the tense comes from the active verb damaged
• Writing was damaged, which does not agree with the plural many houses

No directly related past PYQ was found.