Jack narrowly fell off the cliff but managed to until help came.A. keep onB. hang onC. li

问题补充：

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

A. keep on

B. hang on

C. live on

D. count on

答案：

A. keep on

(答案→)B. hang on

C. live on

D. count on

解析：句意：杰克差一点就从悬崖上掉下去了，但是他设法停住了直到有人来帮忙。keep on继续； hang on停住； live on以……为食； count on指望，依靠。根据句意故选B。