卵泡闭锁可以发生于任何发育阶段的卵泡。

The great invention he made _____ of great benefit to the whole world.[      ]

A. is proved

B. has proved

C. has been proved

D. is proved to be

.

Just because they make more money than I do, ___________they seem to look down on me.

A．so

B．and

C．but

D．不填

颜料制备时，要进行煅烧，其目的是有利于粉碎。

书面表达（满分25分）

假如你叫李华，上周来自美国Hingham中学的交换学生Tim到你们学校访问，作为接待家庭，你参加了这次活动。请根据以下四幅图的先后顺序，介绍参加这次活动的完整过程，给学校英文投稿。

注意：

1．文章开头已为你写好，不计入总词；2．词数不少于100。

We had some American exchange students in our school last week. As a host brother. I’d like to share some happy experiences with you.

慢性风湿性瓣膜病中联合瓣膜病变常发生于

A．二尖瓣和三尖瓣

B．尖瓣和主动脉瓣

C．三尖瓣和主动脉瓣

D．三尖瓣和肺动脉瓣

E．主动脉瓣和肺动脉瓣