根据中文意思和英文提示词语，写出四句语法正确、意思连贯的话。

上周六王明跟同学们到郊外玩，中午他和同学们一起在树下吃饭，饭后他们……

1. last Saturday, Wang Ming, go outing, with his classmates

2. they, have lunch together, under a tree

3. after lunch, there be, some rubbish around them

4. they, not go, until, they, clean up the rubbish