Question

30. this is one ofthe best books ______ on the subject.

30. this is one ofthe best books ______ on the subject.
A)that have everbeen written
B)which have everbeen written
C)that has everbeen written
D)whatever havebeen written

请问答案为什么选A，请帮我详细的解答，谢谢~

Answer 1

选A。限制性定于从句中，引导定语的that 和 which 在许多条件下可以互换，但是在有些条件下就不行。
本题中存在最高级 the best 因此只能用that

Answer 2

首先best 是最高级，一定是填that，所以BD排除~
接着此定语从句的先行词是the best books，是复数，因此从句谓语用的是have~
所以选择A~
希望能帮到你~