Answer:
b. The cake was baked by my grandmother.
Explanation:
A shift in the voice of the verb in a sentence is indicative of whether it is in the active/ direct or passive voice. Passive voice refers to the way the speech is reported, and in this voice, the subject is acted upon by the verb. Simply put, in passive voice, the emphasis is on the recipient of the verb whereas active voice emphasizes the doer of the action.
Among the given sentences, the sentence that uses the verb in the passive voice is option b. In this sentence, the subject "cake" is acted upon by the verb "baked".
Thus, the correct answer is option b.