Select the option that expresses the given sentence in passive voice.

The mechanics are repairing the trucks.

The correct answer is The trucks are being repaired by the mechanics.

Explanation:
The given sentence, "The mechanics are repairing the trucks," is in the present continuous tense in active voice.

To convert a sentence in the present continuous tense from active voice to passive voice, use the following structure:
Active Voice: Subject + is/am/are + Verb (-ing) + Object
Passive Voice: Object + is/am/are + being + Past Participle (V3) + by + Subject

Step-by-step conversion:
1. Identify the object of the active sentence ("the trucks") and make it the subject of the passive sentence.
2. Since the new subject "the trucks" is plural, use the auxiliary verb "are".
3. Add "being" to indicate the continuous action.
4. Change the verb "repairing" to its past participle form, "repaired".
5. Add "by" followed by the original subject ("the mechanics").

Combining these steps gives: "The trucks are being repaired by the mechanics."