样品总件数为X，如300≥X＞3时，取样原则为（）
A．按随机取样
B．每件取样
C．按随机取样
D．按随机取样
E．按随机取样
参考答案：A
一过性脑功能障碍，昏迷时间在半小时以内，查体及辅助检查无异常发现，应诊断为()出血来源主要为脑膜中动脉的是()
A.脑震荡
B.脑挫裂伤
C.原发性脑干损伤
D.急性硬脑膜外血肿
E.慢性硬脑膜下血肿
— What are the _______ doing there?
— They are busy _______ their science experiment.
A．Boys students; to do
B．Boy students; to do
C．Boys students; doing
D．Boy students; doing
随机取样
随机取样机取样随机取样
随机取样随机取样机取样随机取样