A horizontal force $10\, N$ is applied to a block $A$ as shown in figure. The mass of blocks $A$ and $B$ are $2\, kg $ and $3 \, kg $ respectively. The blocks slide over a frictionless surface. The force exerted by block $A$ on block $B$ is :

6 N

The correct answer is option (3) : 6 N

$F=(M_1+M_2)a$

$a=\frac{10}{2+3}=2ms^{-2}$

$F'=M_2(2)=3×2N=6\, N$