Hint: Use formula of force on the particle by dipole
Step 1: Formula used:
Force on particle by dipole is given by the formula:
Electric filed due to dipole on axial condition is given by:
Step 2: Conclusion:
So, force is proportional to the cube of distance inversely.
If the distance is doubled, then force will be time of the original force.
Hence, option A is the correct answer.