Like other amphibians, the wood frog (Rana sylvatica) is unable to generate its own heat, so during periods of subfreezing
temperatures, it ______ by producing large amounts of glucose, a sugar that helps prevent damaging ice from forming inside
its cells.
had survived
survived
would survive
survives
Choice D is the best answer. The convention being tested is the use of verbs to express tense. In this choice, the present
tense verb “survives” correctly indicates that the wood frog regularly survives subfreezing temperatures by producing large
amounts of glucose.
Choice A is incorrect because the past perfect verb “had survived” doesn’t indicate that the wood frog regularly survives
subfreezing temperatures by producing large amounts of glucose. Choice B is incorrect because the past tense verb
“survived” doesn’t indicate that the wood frog regularly survives subfreezing temperatures by producing large amounts of
glucose. Choice C is incorrect because the conditional verb “would survive” doesn’t indicate that the wood frog regularly
survives subfreezing temperatures by producing large amounts of glucose.