称重式灌装机使用的是重量传感器，为保证其精确度，不用时要处于空载状态。
参考答案：对
He can't come to the party. He_______ stay at home.[ ]
A. has
B. have to
C. have
D. has to
简述1922年新学制的主要内容及历史地位。
