流行病学中的偏倚是指()。
A.抽样误差
B.系统误差
C.随机误差
D.错误
E.逻辑误差
参考答案:B
—Do you think we should accept that offer?
—Yes, we should, for we _________ such bad luck up till now, and time _________ out.
A.have had; is running
B.had; is running
C.have; has been run
D.have had; has been run
国家实行配额或许可证管理的商品在进出口通关时,必须要向海关提交《进口货物许可证》或者《出口货物许可证》,无许可证的,视情况决定是否办理进出境海关手续。( )