Two similar gold spheres are separated by a distance of
.34 m. The first sphere (A) has a charge of -4.0 x 10^-8C
and the second sphere (B) has a charge of -5.0 x 10^-13
C. If the electrostatic Force on B due to A is 2.5 N, what is
the magnitude of the electrostatic force on A due to B?

A.10.N

B.5.0 N

C.1.2 N

D.2.5 N

The answer to your question is the letter D. 2.5 N

Explanation:

The electrostatic force is the same in both directions,

If the electrostatic force on B due to A is 2.5 N, the magnitude of the electrostatic force on A due to B must be 2.5N.

Maybe the direction is different but the magnitude is the same.

probably not if net force is zero