磨机中研磨体的状态有（）、（）和（）三种形式。

睾丸细胞染色体畸变试验首选的实验动物是（）

A.地鼠

B.小鼠

C.豚鼠

D.家兔

E.狗

-I went to see you yesterday evening. But you weren't in. Where were you then?

-I ___________ a walk by the lake with my husband.

                                                                                                                                                        [ ]

A. was having

B. am having

C. have had

D. have

太阳和地球间的距离为，阳光从太阳照射到地球所需的时间约为 _______秒。

直流发电机的容量越大，发生的电压越高。（）

压装轴承内圈的设备及装配工具是什么？