In Dulce et Decorum Est, hags is used to describe young soldiers. The simile 'coughing like hags' was used because the young soldiers went into battle strong and full of life. After battle, they returned looking aged and beat down - hence 'hags' or resembling beggars.
This sentence would probably be a citation in APA style. Citations on research papers are very important since they give due credit to the original owner of the statement. Statements that don't have citations tells the readers that those statements are of the researcher/s alone which would be a problem for them if found out that it wasn't theirs to begin with. This would result to a work of plagiarism which is a grave sin in constructing research papers and is more equated with the act of stealing.
Answer:
C because rather is telling you why it's not a valley (hope I made it make sense)