JEE Main Physics question

A block of mass 'm' is connected to another block of mass 'M' by a massless spring of spring constant K. The blocks are kept on a smooth horizontal plane. Initially, the blocks are at rest, and the spring is unstretched. Then a constant force F starts acting on the block of mass 'M' to pull it. Find the force on the block of mass 'm' (at the instant both blocks share a common acceleration, i.e., via the overall centre-of-mass motion).

• (A)mF/M
• (B)(M+mF)/m
• (C)mF/(m+M)Correct
• (D)MF/(m+M)