JEE Main Physics question

A block of mass M placed on a frictionless horizontal table is pulled by another block of mass m hanging vertically by a massless string passing over a frictionless pulley. The tension in the string is [MP PET 2010]

• (A)Mm g/(M+m)Correct
• (B)M/(M+m) · g
• (C)(M+m)/(Mm) · g
• (D)Mm/(M+m)