问题补充：
--- Do you have any idea why the bus – drivers are on strike?
--- As far as I know, they are a pay rise.
A. calling off
B. calling at
C. calling in
D. calling for
答案：
A. calling off
B. calling at
C. calling in
(答案→)D. calling for
解析：可联系答案网客服索取。
