老师请问这题为什么选B啊，A为什么不对？

问题如下：

Question A parametric test is most likely preferred to a non-parametric test when:

选项：

A.the data are given in ratio or ordinal scale.

B.defined sets of assumptions are given.

C.the population is heavily skewed.

解释：

B is correct. A parametric test is more appropriate than a non-parametric one when an analyst is concerned with parameters whose validity depends on a definite set of assumptions—for example, assumptions about the distribution of the population producing the sample.

A is incorrect. A nonparametric test is suitable for this case.

C is incorrect. A nonparametric test is also suitable for this.