统计的四个要素是()。
A.总体、样本、标志和指标
B.总体、样本、推断和推断的可靠性
C.总体、总体单位、标志和指标
D.标志、指标、变量和变异
参考答案:B
皱纹金属套机
Which of the following is not a factor which can interfere with the pulse of sound and cause a variation the depth reading?()
A.salinity
B.temperature
C.the hydrostatic pressure
D.Vessel’s speed