a
Given, Three point charge \(q_1, q_2\), and \(q_3\).

Let \(F\) be Force exerted by \(q_1\) on \(q_2\).

To find \(F\) when \(q_3\) is close to \(q_2\).

We know,

As the principal of superposition states that the Force exerted by a charge on another point is independent of the presence of the other charges and the net force on a point chorge due to the number of charges will be the vector sum of the forces exerted by the other charges.

despite of the presence of the \(3^{\text {rd }}\) charge \(q_3\), the Force \((F)\) exerted by the charge \(q_1\) on charge \(q_2\) will remain unchanged.

However, the net force experienced by the charge \(q_2\), will change due presence of \(q_3\).