（）和（）间的差数叫做上偏差。
A.最大极限尺寸
B.基本尺寸
C.标准尺寸
D.非标准尺寸
参考答案：A, B
中频段
73. She________the children round him and asked them to listen to her attentively.
A．gathered
B．collected
C．told
D．Drew
