It's necessary to use a/an _______ when a quotation is introduced by a verb.

A. quotation mark
B. comma
C. ellipse
D. colon

http://www.gallaudet.edu/tip/english-center/writing/quoting-and-praphrases.html

The correct answer is B. comma.

When a quotation is introduced by a verb, it is necessary to use a comma before the quotation begins. This is a common rule in punctuation and grammar.

To get to this answer, you would need to understand the basic rules of punctuation when it comes to using quotations. In this case, the question is specifically asking about the introduction of a quotation by a verb. Knowing that, you can eliminate options C and D (ellipsis and colon) because they are not typically used to introduce a quotation. You are left with options A and B.

To determine the correct choice between quotation mark (Option A) and comma (Option B), you need to know that a comma is the appropriate punctuation to separate the introductory verb from the quotation. Therefore, the correct answer is B. comma.

Colon