The committee insisted on a total check on all social evils and he was the one who heralded the revolution.

The correct answer is A. Harbinger.

A harbinger is a person or thing that indicates the approach of something important or momentous. In this case, the committee is insisting on a total check on all social evils, which indicates that a revolution is about to happen.

The other options are incorrect because they do not accurately describe the person in the question.

• An apostate is a person who renounces a religious faith.
• A renegade is a person who deserts his party, cause, or principles.
• An apostle is a person who is sent on a mission to spread a particular belief or doctrine.