After a long walk they pass over the mountain.Acould be able toB. canC. wouldD. were

问题补充：

After a long walk, they pass over the mountain.

Acould be able to

B. can

C. would

D. were able to

答案：

A. could be able to

B. can

C. would

D. were able to

解析：辨析be able to 与can ;由语境可知：关键是走了很长的路，表示一段过程不容易