活塞式压缩机按汽缸的排列方式分，（）活塞式压缩机的汽缸中心线平行于地面。
A、对置式
B、对称对置式
C、卧式
D、立式
参考答案：C
空间某一静电场的电势φ在x轴上分布如图所示，x轴上两点B、C点电场强度在x方向上的分量分别是EBx、Ecx，下列说法中正确的有（ ）
A．B、C两点的电场强度大小EBx＜Ecx
B．EBx的方向沿x轴正方向
C．电荷在O点受到的电场力在x方向上的分量最大
D．负电荷沿x轴从B移到C的过程中，电场力先做正功，后做负功
句型转换。
1. Let the boy in. （改为否定句）
______ ______ the boy in.
2. Today is a good time to have the party. (对划线部分提问)
______ ______ a good time to have the party?
3. Tom is going to work hard. His dream will be able to come true. （用if合并句子）
______ Tom ______ hard, his dream ______ be able to come true.
4. If you go to the movies with us, you will have fun. （改为同义句）
If you go to the movies with us, you will ______ ______ ______ ______.
5. Get up quickly, or you will miss the school bus. (改为同义句)
______ you ______ get up quickly, you ______ ______ the school bus.
