Which of the following statement(s) is/are correct?

If charges are of opposite signs, then the two fields are along the same direction. So, they cannot be zero. Hence, the charges should be of same sign. Therefore, option (c) is correct. Further, work done by external force = change in potential energy $$\begin{aligned}& \therefore \quad W_{A → B}=q(\DeltaV) \\ & =(+1)\left(V_B-V_A\right) \\ & \text{ or } \quadW_{A → B}=V_B-V_A \\ & \end{aligned}$$Therefore, option (d) is also correct. $\therefore$ Correct options are (c) and (d). Analysis of Question (i) Question is simple. (ii) $W=\Delta U$ (by external force) If charge is just moved, without changing the kinetic energy. If nothing is mentioned in the question regarding the kinetic energy then we take $W=\Delta U$.