Check all of the following that are proper units for measuring length in the U.S. system of units.

The discriminant tells us how many real solutions there are. Since the parabola doesn't have any x-intercepts, the discriminant is less than zero, and therefore is answer A.

If a discriminant is:
>0, there are 2 x-intercepts
=0, there is 1 x-intercept
<0, there are no x-intercepts