I didn’t go outing on National Day because the bad weather the difficulty.A. added upB. a

问题补充：

I didn’t go outing on National Day because the bad weather the difficulty.

A. added up

B. added

C. added up to

D. added to

答案：

A. added up

B. added

C. added up to

(答案→)D. added to

解析：考查add的用法。句意“我国庆节没有去远足，因为糟糕的天气徒增了难度。”add up“加起来，有意义”；add up to“合计达，意味着”；add to“增加”。故选D。