Concept:In active voice, the subject performs the action. In passive voice, the subject receives the action and often includes a form of "be" plus past participle.
Explanation:Check each option for passive markers (be + V3).
Option A: "have your eyes tested" uses a special passive structure (have/get + object + V3). It is passive.
Option B: "has been altered" uses "been + altered" – passive.
Option D: "had been cut" uses "been + cut" – passive.
Option C: "Boys could not have done" has no form of "be" before a past participle. The subject "boys" performs the action. Hence it is active.
Only option C is in active voice.
Answer:C. Boys could not have done all this damage.