Answer:
(C) consider.
Explanation:
In this scenario, the professor has an intense knowledge of the playwright’s works, and he will not entertain any doubt concerning their authorship.
In the lines above, "entertain" most nearly means consider.
The professor having an intense knowledge simply means that he has an excessive or extreme level of knowledge of the playwright’s works. Therefore, with this high degree of knowledge about the work, he would not entertain or consider any doubt concerning their authorship.
In this context, to entertain simply means to hold an idea in one's mind, think about, have in mind, or to be willing to consider an idea.
Hence, the most appropriate word that is nearest in meaning to "entertain" in the above statement is "consider."