Each of the book’s protagonists—Mark Streit, Mary Eby, and Dr. Thomas—has ... ...

Determine whether or not there is an error in the underlined portion of the sentence above. If there is no error, select answer choice "A".
(A) Each of the book’s protagonists—Mark Streit, Mary Eby, and Dr. Thomas—has
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Press: Set B - Subject-Verb Agreement