我会背，我会填。

                                                                       所见      

                                                                牧童骑_____，     

                                                                歌___振__樾。     

                                                                意欲捕鸣蝉，     

                                                                忽然_______。

加氢改质装置的降凝催化剂是（）形。

A.拉西环

B.圆柱

C.三叶草

D.球