The sun never sets during the Arctic summer in the Far North. In response, reindeer in this region must change their sleep
habits. Instead of resting when it gets dark, they rest when they need ______ their food.
digest
will digest
to digest
digesting
Choice C is the best answer. The convention being tested is the use of nonﬁnite verb forms within a sentence. Working
together with the ﬁnite verb "need," the nonﬁnite to-inﬁnitive verb "to digest" is correctly used to form a subordinate clause
that describes what the reindeer need.
Choice A is incorrect because the verb "digest" (in either its ﬁnite or nonﬁnite form) can’t be used in this way with the ﬁnite
verb "need." Choice B is incorrect because the ﬁnite verb "will digest" can’t be used in this way with the ﬁnite verb "need."
Choice D is incorrect because the nonﬁnite participle "digesting" can’t be used in this way with the ﬁnite verb "need."