og214 选项中的people

Although the term "psychopath" is popularly applied to an especially brutal criminal, in

psychology it is someone who is apparently inca­pable of feeling compassion or the pangs

of conscience.

(A)  it is someone who is

(B)   it is a person

(C)  they are people who are

(D)  it refers to someone who is

(E)   it is in reference to people

答案是D. og中有一句这样的解释：E omits a main verb, such as

applied, that, in grammatical context here, is required after is. Also, the

word people incorrectly shifts number from singular to plural.

就是说people从来就当复数看，没有单数的意义是么？

谢谢！