齿轮泵主要由泵体、主动齿轮、从动齿轮、（）前后盖板、传动轴及安全阀组成。
A、密封垫
B、联轴号
C、挡套
D、轴承
参考答案：D
按期货交易环节划分有( )风险。
A．代理
B．交易
C．交割
D．客户
A．He was able to talk again.
B．He raced to the nursing home.
C．He could tell red and blue apart.
D．He could not recognize his wife.
