Change the following from active to passive: They should be auditing the subsidiary accounts this quarter.

Correct — C. The active verb is should be auditing: modal + be + -ing. A voice change keeps the modal and the progressive, and turns the main verb into a past participle.

Modal kept: should be
Progressive kept: being
Main verb as past participle: audited

The object becomes the subject: 'The subsidiary accounts should be being audited by them this quarter' → option (c).

Why the others are wrong

• (a)
  The subsidiary accounts should have been audited by them this quarter. — Should have been audited is the perfect passive. It turns the meaning into a past obligation, should have done, and drops the progressive of should be auditing.
• (b)
  The subsidiary accounts are being audited by them this quarter. — Are being audited drops the modal should, turning a duty into a statement of what is happening now.
• (d)
  The subsidiary accounts should be audited by them this quarter. — Should be audited is the passive of should audit. It keeps the modal but loses the progressive, so the -ing of be auditing disappears.

A voice change keeps the modal, tense and aspect of the active verb. The passive adds be + past participle, and a progressive shows up as being.

should audit → should be audited
should be auditing → should be being audited
should have audited → should have been audited

The object, the subsidiary accounts, becomes the subject, and they becomes by them.

Key facts

• Modal progressive passive: modal + be + being + past participle (should be being audited).
• Modal simple passive: modal + be + past participle (should be audited).
• Modal perfect passive: modal + have been + past participle (should have been audited).

Common traps

• Choosing should be audited because be being looks wrong, and losing the progressive of be auditing.
• Adding being when the active has no -ing: should clean becomes should be cleaned, not should be being cleaned.

No directly related past PYQ was found.