Please answer the question with appropriate explanation thanks

@Chandan Kumar.For solving this question you can use the potential enerdy of a dipole in a uniform electric field which is given as 

                                       

so using this relation you can conserve total energy as there is no external work done.Initial total energy will only include potential energy where as the final total energy will include both potential as well as kinetic energy.Hence you can solve question as given in the image below

Hope it helps.