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

1. A
   zero
2. B
   $4\text{N}$
3. C
   $6\text{N}$
4. D
   $10\text{N}$