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！

单数的是民族,部落,种族.