@Richmond, this is a principle question, so you're looking for the answer that would explain why the author is making the conclusion put forward in the argument.
In this case we have an archaeologist who is arguing that an offer from a large corporation to build a public restoration of an archeological site should be rejected because "many parts of the site contain unexamined evidence." This is the only reason for rejecting a proposal that otherwise seems like a good project, so what principle would drive the archaeologist to this conclusion?
(A) the argument says nothing of ownership, so this is irrelevant.
(B) the argument seems to suggest that the restoration would be of the most ideal period, so this doesn't explain the archaeologist's opposition to the project.
(C) the archaeologist says nothing that suggests that he or she has a problem with the content or period of the project.
(D) the archaeologist says nothing to call the large corporations motivations into question. It doesn't seem to matter whether the corporation stands to profit or not.
(E) directly gets that the "because" statement after the archaeologist's conclusion. Building on top of the existing site would risk damaging or losing the unexamined evidence that remains on site. Since the archaeologist argues that the project should not move forward "because" there remains unexamined evidence, it suggests that the archaeologist values the unexamined evidence over the displaying of preexisting theories, and THAT is the principle behind the archaeologist's conclusion.
