平板阀在关闭到位后，回旋1/4~1/2圈是为了保证阀的浮动密封。（）
A、对
B、错
参考答案：A
The reason being late for the meeting was his little son fell in this morning.
A．for; that
B．why; that
C．for; because
D．why; because
商品的二重性是指价值与交换价值。 ( )
