Dr. Rocío Paola Caballero-Gill is a paleoceanographer. This means that Dr. Caballero-Gill doesn’t just study oceans as they
are today. She uses chemistry and fossil evidence ______ oceans as they were in the past.
has studied
to study
studied
studies
Choice B is the best answer. The convention being tested is the use of verb forms within a sentence. The nonﬁnite to-
inﬁnitive verb “to study” is correctly used to form a subordinate clause that indicates what Dr. Caballero-Gill uses chemistry
and fossil evidence for (to study oceans as they were in the past).
Choice A is incorrect because it results in an ungrammatical sentence. The ﬁnite verb “has studied” can’t be used in this way
to form a subordinate clause that indicates what Dr. Caballero-Gill uses the evidence for. Choice C is incorrect because it
results in an ungrammatical sentence. The ﬁnite verb “studied” can’t be used in this way to form a subordinate clause that
indicates what Dr. Caballero-Gill uses the evidence for. Choice D is incorrect because it results in an ungrammatical
sentence. The ﬁnite verb “studies” can’t be used in this way to form a subordinate clause that indicates what Dr. Caballero-
Gill uses the evidence for.