A、  B、  C、  C(A)适合用来回答why疑问句。(B)使用与course的意思接近的field，设置陷阱。(C)指明了具体的数字，故为正确答案。

Ms. Ward gave you the entire report, didn’t she?
(A)Yes, I’m tired.
(B)No, one section is missing.
(C)Could you pour me another cup?

How often do you have a training course?
(A)Sometimes to inspect the course.
(B)Of course, they are in a different field.
(C)Three times a year.