Which of the following statement about abstract is NOT correct?

Which of the following statement about abstract is NOT correct?
A.An abstract contains key words found in a research paper, thesis, or review.
B.Components of an abstract vary according to different disciplines.
C.An abstract is an excerpted passage from a research paper, thesis, or review.
D.The length of abstracts varies according to discipline and the length of the work.
正确答案：An abstract is an excerpted passage from a research paper, thesis, or review.