the mountains was hard work for them but as they looked around, they could not help screaming.
A. Climb
B. To climb
C. For climbing
D. They climbed
网友回答
A. Climb
(答案→)B. To climb
C. For climbing
D. They climbed
解析：考查非谓语动词。句意：爬上山顶对于他们来说是一项艰苦工作，但是当他们看了看四周时，他们忍不住尖叫起来。不定式表示具体的将要进行的动作，结合语境可知选B。