In 1990, California native and researcher Ellen Ochoa left her position as chief of the Intelligent Systems Technology Branch
at a NASA research center ______ the space agency’s astronaut training program.
to join
is joining
joined
joins
Choice A is the best answer. The convention being tested is the use of nonﬁnite verb forms in a sentence. The nonﬁnite to-
inﬁnitive verb "to join" is correctly used to form a subordinate clause that expresses why Ochoa left her position (to join the
training program).
Choice B is incorrect because the ﬁnite verb "is joining" can’t be used in this way to indicate Ochoa’s action of joining the
training program. A conjunction such as "and" would be needed to coordinate "is joining" with the previous ﬁnite verb, "left."
Choice C is incorrect because the ﬁnite verb "joined" can’t be used in this way to indicate Ochoa’s action of joining the
training program. A conjunction such as "and" would be needed to coordinate "joined" with the previous ﬁnite verb, "left."
Choice D is incorrect because the ﬁnite verb "joins" can’t be used in this way to indicate Ochoa’s action of joining the training
program. A conjunction such as "and" would be needed to coordinate "joins" with the previous ﬁnite verb, "left."