The correct answer is D. speaker.
An orator is a person who gives speeches, especially in public. A critic is a person who judges the quality of something, especially art, literature, or a performance. A debater is a person who takes part in a formal debate. A singer is a person who sings.
In the given question, the person was adjudged as the best orator of the college. This means that he was judged to be the best speaker in the college. The other options are not relevant to the question, as they do not involve speaking.
