用显微镜观察洋葱表皮细胞，不易观察清楚的结构是（　　）

A．细胞壁

B．细胞膜

C．细胞核

D．液泡

Don't _________ what he said. I think we can try it again.    [ ]

A. argue with                

B. complain about    

C. get on                    

D. be angry with