Alex made the ruler shown.

The unit of the ruler, n, is a rational number.
The variable x describes an irrational length.

Which of the following can describe the length 4x?


A. 4x must be irrational, because a nonzero, rational number times an irrational number is always irrational.

B. 4x can be either rational or irrational, because x is not located on a tick mark on the ruler.

C. 4x can be either rational or irrational, because each tick mark on the ruler is a fraction of n.

D. 4x must be rational, because a nonzero, rational number times an irrational number is always rational.