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.

Which choice completes the text so that it conforms to the conventions of Standard English?
Choose 1 answer:
Choose 1 answer:
(Choice A) to join
A
to join
(Choice B) is joining
B
is joining
(Choice C) joined
C
joined
(Choice D) joins
D
joins