下列仪器中，需要每半年校验一次的有（）。
A.回弹仪
B.原位轴压仪
C.经纬仪
D.水准仪
参考答案：A, B
He ___ when we came
A．will arrive
B．had already arrived
C．would alreay arrive
D．has already arrived
猩红热的皮疹出现在发热后
A．12h之内B．12～48hC．61～72hD．49～60hE．大于72h
