JEE Main Physics question

A big ball of mass M, moving with velocity u, strikes a small ball of mass m, which is at rest. Finally the small ball obtains velocity u and the big ball obtains velocity v. Then what is the value of v?

• (A)(M−m)/(M+m) × uCorrect
• (B)[2m/(M+m)] × u
• (C)(M+m)/(M−m) × u
• (D)[M/(M+m)] × u