Answer
A./C.
Work Step by Step
The back of the textbook says that A. is the correct answer, which could be the case if the similar realized niches were not exactly the same; one species could shift its realized niche and both could coexist, like the case of the coexisting Paramecium species (p. 1191). Much more likely is C. There is not reason for B. to occur, and D. is wrong, based on the Paramecium example already mentioned.
