A block of metal weighing 2 kg is resting on a frictionless plane. It is struck by a jet releasing water at the rate of \[1\text{ }kg\text{ }{{s}^{-1}}\] and at a speed of\[5\text{ }m\text{ }{{s}^{-1}}\]. The initial acceleration of the block is

• A. \[7.5\text{ }m\text{ }{{s}^{-2}}\]               
• B. \[1.25\text{ }m\text{ }{{s}^{-2}}\] 
• C. \[5\text{ }m\text{ }{{s}^{-2}}\]      
• D.        \[2.5\text{ }m\text{ }{{s}^{-2}}\]