Myra is writing a research paper about how mark twain's personal life influenced his writing. which of the following are secondary sources that she could use for evidence in her paper?
a a magazine article about mark twain
b the novel adventures of tom sawyer by mark twain
c the autobiography of mark twain
d the novel life on the mississippi by mark twain
e an essay about mark twain by a literary critic

A a magazine article about Mark Twain

E an essay about Mark Twain by a literary critic

This question is asking for more than one answer because it says 'Which of the following are secondary sources'
Secondary sources refers to those documents that relate or discuss information that are originally presented somewhere else. In contrast a primary source is an original source of the information that is been discussed. Thus, for the question given above, the secondary sources refers to those books that are not written by Mark Twain [THAT IS OPTION A AND E] while the primary sources are the books written by Mark Twain himself [THAT IS OPTION B,C AND D].
Therefore, the correct options for this question are OPTION A AND E.