Which choice completes the text so that it conforms to the conventions of Standard English?
A
were
B
have been
C
are
D
was
Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is subject-verb agreement. The singular verb "was" agrees in number with the singular subject "amplifying." Gerunds such as "amplifying" are always singular.
Why the other choices are wrong
Choice A
Choice A is incorrect because the plural verb "were" doesn’t agree in number with the singular subject "amplifying."
Choice B
Choice B is incorrect because the plural verb "have been" doesn’t agree in number with the singular subject "amplifying."
Choice C
Choice C is incorrect because the plural verb "are" doesn’t agree in number with the singular subject "amplifying."