Question

ignore the pencil marks

Answer 1

Firstly Let's say a Force F was applied on the rope actually the whole system
cuz if u pull the rope the block comes along with it
So now to find the force exerted by rope on the block
Force on the block=Mass of Block*acceleration of system(this is because the system moves together)
Neither does the rope or block move individually
So acceleration of system=Net force/Net mass
=F/M+m
So force on the block=M*acceleration of system
=M*F/(M+m)
So the answer is option A
Hope it helps
:)

Answer 2

hope u will understand..if prblm..query in cmnt box