--Sorry I have to now It is time for class．- OK I’ll call back later．A. hang upB. b

问题补充：

--Sorry, I have to now． It is time for class．

--- OK, I’ll call back later．

A. hang up

B. break up

C. give up

D. hold up

答案：

(答案→)A. hang up

B. break up

C. give up

D. hold up

解析：短语辨析。A． 搁置；拖延；挂断电话 B．打碎；结束 C．放弃 D． 举起；阻拦。根据题意，对不起我不得不挂断电话了。该上课了。——好吧，稍后我打给你。故选A。