Select the option that expresses the following sentence in passive voice. The baker baked the cake.

Correct — D. The active sentence is simple past: baked. A change of voice never changes the tense, so the passive has to be simple past passive — was/were + past participle.

The object, the cake, becomes the subject and is singular, so the auxiliary is was. The old subject follows behind by: the cake was baked by the baker.

That is option (d).

Why the others are wrong

• (a)
  The cake had been baked by the baker. — Had been baked is past perfect passive. The active verb is a plain simple past, so this pushes the baking further back than the original sentence puts it.
• (b)
  The cake has been baked by the baker. — Has been baked is present perfect passive, which ties the baking to now. The active sentence is simple past and claims no connection to the present.
• (c)
  The baker has been baking the cake. — The baker has been baking keeps the baker as the subject, so it is still active — and it changes the tense to present perfect continuous on top of that.

Voice change follows a fixed procedure. The object becomes the subject, the verb becomes the matching form of be + past participle, and the old subject moves behind by.

What decides this item is the auxiliary, because be has to carry the tense of the original verb.
Simple past baked gives was baked.
Simple present bakes gives is baked.
Present perfect has baked gives has been baked.

Get the tense right and here one option is left standing.

Key facts

• The passive swaps subject and object, uses the right form of be with the past participle, and puts the agent after by.
• A simple past active becomes was or were plus the past participle, not has been or had been.
• The auxiliary agrees with the new subject: the cake was baked, the cakes were baked.

Common traps

• Choosing a perfect form because it sounds more formal than was baked
• Picking an option that is still active because it contains been or being

No directly related past PYQ was found.