B不是曲线的意思吗？

问题如下：

Which one of the following statements concerning chi-square and F-distributions is false?

选项：

A.

They are both asymmetric distributions.

B.

As their degrees of freedom increase, the shapes of their pdfs become more bell curve-like.

C.

The domains of their pdfs are positive and negative numbers.

解释：

C is correct, since it is false. Both chi-square and F-distributions are bounded from below by zero, so the domains of their pdfs are restricted to positive numbers