Which choice completes the text so that it conforms to the conventions of Standard English?
A
is increasing
B
increase
C
increases
D
has increased
Explanation
Correct answer: B.
Choice B is the best answer. The convention being tested is subject-verb agreement. The plural verb "increase" agrees in number with the plural subject "toxins."
Why the other choices are wrong
Choice A
Choice A is incorrect because the singular verb "is increasing" doesn’t agree in number with the plural subject "toxins."
Choice C
Choice C is incorrect because the singular verb "increases" doesn’t agree in number with the plural subject "toxins."
Choice D
Choice D is incorrect because the singular verb "has increased" doesn’t agree in number with the plural subject "toxins."