We meant to finish the work by dark but we were so tired that we could not .A. hold onB.

问题补充：

We meant to finish the work by dark, but we were so tired that we could not .

A. hold on

B. last on

C. carry on

D. keep to

答案：

(答案→)A. hold on

B. last on

C. carry on

D. keep to

解析：根据前面说到我们很累，所以这里用hold on表示：（在困境或危险中）坚持住，挺住