【简答题】What is the difference between a discrete numerical variable and a continuous numerical variable?
【单选题】According to the passage,the numerical value Of the concentration level of a substance is only useful if
A.
the other substances in the area are known
B.
it is a localized area
C.
it can be calculated quickly
D.
the naturally occurring level is also known
【单选题】将下列选项中的词语依次填入各句括号处,最恰当的一组是: ①遍地的春花同心花()开放。 ②人和行李()到了,一件都没少。 ③我明天进城,咱们()去吧。