【单选题】计算以下10个玉米果穗长度(cm)( 19、21、20、20、18、19、22、21、21、19)的平均数和标准差为:
【单选题】Which animal is probably the original source of virus?
【单选题】The ()in the river has to be rebuilt.
【单选题】若|2000x+2000|=20×2000,则x等于( )
【判断题】客户关系管理是理念、技术和实施的综合使用。
【单选题】This smoke signal has passed its expiry date,and become damp and ineffective
A.
This smoke signal is damp but still effective
B.
This smoke signal is not damp but not effective
C.
This smoke signal is expired but still effective
D.
This smoke signal is expired and not effective