导言中应包括按主题字母顺序排列的索引。
A The introduction should be included in an alphabetical index by subject.
B An alphabetical index by subject is to be included in the introduction.
C The introduction includes an alphabetical index subject.
A The introduction should be included in an alphabetical index by subject.
B An alphabetical index by subject is to be included in the introduction.
C The introduction includes an alphabetical index subject.