使用代理服务器技术时内部网络只接受（）提出的服务请求，拒绝外部网络其他结点的直接请求。
参考答案：代理
读句子，选答语。
( )1. Can I help you?
( )2. What size?
( )3. Are they nice?
( )4. How much are they?
( )5. Are they all right?
A. Yes, please.
B. They're thirty yuan.
C. Size seven.
D. Yes, they are.
E. Yes, they are very nice. I like them.
多级泵轴间推力的平衡方法，一般采用（）。
A.平衡盘
B.平衡孔
C.平衡管
