In winter, the diets of Japanese macaques, also known as snow monkeys, are inﬂuenced more by food availability than by
food preference. Although the monkeys prefer to eat vegetation and land-dwelling invertebrates, those food sources may
become unavailable because of extensive snow and ice cover, ______ the monkeys to hunt for marine animals in any streams
that have not frozen over.
forces
to force
forcing
forced
Choice C is the best answer. The convention being tested is the use of ﬁnite and nonﬁnite verb forms within a sentence. The
nonﬁnite present participle “forcing” is correctly used to form a participial phrase that supplements the main clause
“those...cover,” describing the effects on monkeys of the lack of food sources.
Choice A is incorrect because the ﬁnite present tense verb “forces” can’t be used in this way to supplement the main clause
(“those...cover”). Choice B is incorrect. While the nonﬁnite to-inﬁnitive “to force” could be used to form a subordinate clause
that supplements the main clause (“those...cover”), to-inﬁnitives conventionally express purpose, and nothing in the
sentence suggests that the food sources become unavailable for the purpose of forcing monkeys to hunt marine animals.
Choice D is incorrect because the ﬁnite past tense verb “forced” can’t be used in this way to supplement the main clause
(“those...cover”).