The phenomenon _______ scientists have studied for decades remains unexplained.

7
reading

Which choice completes the text so that it conforms to the conventions of Standard English?

A

who

B

whom

C

that

D

whose

Correct Answer: C

Choice C is the best answer. "That" for things in restrictive clauses.

Choice A is incorrect because "who" is for people. Choice B is incorrect because "whom" is for people. Choice D is incorrect because "whose" shows possession.