All the firemen in the city were ______to fight against the big fire.

A．called in

B．called off

C．called up

D．called on

参考答案

正确答案：C
解析：called in意为“回收”；called off意为“取消”；called up 意为“召集，打电话，使人想起”；called on意为“访问(某人)”。