A block of metal weighing 2 kg is resting on a frictionless plane (as shown in figure). It is struck by a jet releasing water at a rate of 1 kg s$$^{-1}$$ and at a speed of 10 m s$$^{-1}$$. Then, the initial acceleration of the block, in m s$$^{-2}$$, will be

A

3

B

6

C

5

D

4