欧美日韩黄网欧美日韩日B片|二区无码视频网站|欧美AAAA小视频|久久99爱视频播放|日本久久成人免费视频|性交黄色毛片特黄色性交毛片|91久久伊人日韩插穴|国产三级A片电影网站|亚州无码成人激情视频|国产又黄又粗又猛又爽的

The professor can hardly find sufficient grounds         his argument.

A．which to be based on                         B．on which to base

C．which to be based                      D．which to base

The professor can hardly find sufficient grounds          his argument in favor of the new theory.

A．which to base on                                        B．on which to base

C．to base on which                            D．which to be based on

The professor can hardly find sufficient grounds　 ________ his argument in favor of the theory.

A．which to base on　　 B．on which to base

C．to base on which　　 D．which to be based