Answer:
B.) I must cite the research I used in my essay.
C.) The thief returned to the site of the crime.
D.) We caught sight of a whale off the coast.
Step-by-step explanation:
Homophone: Each of two or more words having the same pronunciation but different meanings, origins, or spelling.
  Site: An area of ground on which a town, building, or monument is constructed, or a website.
 Cite: Quote (a passage, book, or author) as evidence for or justification of an argument or statement, especially in a scholarly work.
 Sight: The faculty or power of seeing.