Grumble vi. 发怨言;叽叽咕咕地表示不满(at, about, over); vt.抱怨(out)
He grumbled at/about/over the low pay offered to him.
他抱怨给他的工资低。
grumble one's complaint发牢骚
8. They are endeavoring to change society as a whole.
A.  trying                      B. everlasting
C. doing                        D. making
A.     分析：根据搭配结构特点“..+ to do..”判断A是答案。
Everlasting adj.永恒的, 持久的
Evergreen; now-fertile; never-happening;