Jack almost fell off the cliff but managed to until help came.A. keep onB. catch onC. c

问题补充：

Jack almost fell off the cliff, but managed to until help came.

A. keep on

B. catch on

C. count on

D. hang on

答案：

A. keep on

B. catch on

C. count on

(答案→)D. hang on

解析：hang on(=hold fast, keep hold)牢牢抓住，抓紧不放：Help! I can hang on much longer.(救命啊！我支持不住啦。)keep on(doing sth.)继续（做......）；catch on 理解；count on 指望，依赖。

本题译文：杰克差点从悬崖上掉下来，但得以抓住不放直到得救。