Which best explains why the expression plus or minus StartRoot b squared minus 4 a c EndRoot cannot be rewritten as b plus or minus StartRoot negative 4 a c EndRoot during the next step?

Negative values, like −4ac, do not have a square root.
The ± symbol prevents the square root from being evaluated.
The square root of terms separated by addition and subtraction cannot be calculated individually.
The entire term b2 − 4ac must be divided by 2a before its square root can be determined.