<p>In Jon Krakauer's Into the Wild, the main character and the novelist, who [serves] as the narrator, share a vital experience: At different points, the narrative [depicts] each one in a fight [for][their] life in the Alaskan wilderness. [no error]</p>
<p>Or maybe the character in question is both the main character and the novelist. Either way, it must be correct since the error occurs in choice D.</p>
<p>'serves' is referring to the narrator. You can easily tell by reading the rest of the sentence. If it were [serve] then the following words would have to be [as the narrator*s*]. And since that part of the sentence(the 'as the narrator' part) isn't highlighted or underlined, it is correct in the context of this particular sentence.So we know [serves] is correct.</p>
<p>Ah. When he said "why is serves right?" by mistake I interpreted it as asking"why is serves [the] right [answer]?"
So I read the first line and figured "I guess that's it".
Now I realize that he wanted to know why "serves" was an acceptable part of the sentence.</p>
<p>Sorry I just felt the need to explain myself. Now after having read the sentence fully, both his question and choice D make sense.</p>