OG详解-OG5 文法 Q21

Choice C is the best answer. The convention being tested is subject-verb agreement. The plural verb “underlie” agrees in number with the plural subject “frameworks.”
Choice A is incorrect because the singular verb “underlies” doesn’t agree in number with the plural subject “frameworks.” Choice B is incorrect because the singular verb “is underlying” doesn’t agree in number with the plural subject “frameworks.” Choice D is incorrect because the singular verb “has been underlying” doesn’t agree in number with the plural subject “frameworks.”