下列哪种组成不是荧光显微镜的结构元件（）

A.激发光源

B.二组滤光片

C.二色镜

D.聚光镜

E.环形光阑

Can you please tell me where _      _ the post office ?        [ ]

A. to find                        

B. can I find        

C. how to find                    

D. find