We set off early next morning and came to unknown valley after about an hour.A. the; the

问题补充：

We set off early next morning and came to unknown valley after about an hour.

A. the; the

B. the; an

C. /; a

D. /; the

答案：

A. the; the

(答案→)B. the; an

C. /; a

D. /; the

解析：考查冠词。句意我们第二天造成早早地出发了，在大约一小时后到了一个不知名的山谷。结合语境可知前文特指某个早晨，下文泛指任何一个不知名的山谷，故选B。