题干
--How do you study for a test?
-- I study by asking the teacher help．
A：to
B：for
C：at
D：of
答案(点此获取答案解析）
B
--How do you study for a test?
-- I study by asking the teacher help．
A：to
B：for
C：at
D：of
会产生增根，求 
的值．