An object with a mass 10 kg moves at a constant velocity of 10 m/sec. A constant force then acts for 4 second on the object and gives it a speed of 2 m/sec in opposite direction. The acceleration produced in it, is [CPMT 1971]

• A.                              \[3\,m/{{\sec }^{2}}\]          
• B.                           \[-3\,m/{{\sec }^{2}}\]          
• C.                         \[0.3\,m/{{\sec }^{2}}\]            
• D.                           \[-0.3\,m/{{\sec }^{2}}\]