The correct answer is C. Advocate.
An exponent is a number or variable that indicates how many times another number or variable is multiplied by itself. For example, in the expression $2^3$, the exponent is 3, and the base is 2. This means that $2^3$ is equal to $2\times2\times2$, or 8.
An advocate is someone who speaks or writes in support of a cause or policy. For example, an advocate for animal rights might speak out against animal testing, or an advocate for gun control might write letters to their elected officials urging them to support stricter gun control laws.
The other options are incorrect because they do not accurately describe the meaning of the word “exponent.” A meddler is someone who interferes in other people’s affairs without being asked. To cancel something means to stop it from happening or being used. Horrid means very unpleasant or disgusting.