Which choice completes the text so that it conforms to the conventions of Standard English?
A
have remained
B
remain
C
remains
D
are remaining
Explanation
Correct answer: C.
Choice C is the best answer. This choice uses the singular verb "remains" to match the singular subject "equation."
Why the other choices are wrong
Choice A
Choice A is incorrect. The singular noun "equation" doesn’t match with the plural verb conjugation "have remained."
Choice B
Choice B is incorrect. The singular noun "equation" doesn’t match with the plural verb conjugation "remain."
Choice D
Choice D is incorrect. The singular noun "equation" doesn’t match with the plural verb conjugation "are remaining."