A boy having a mass equal to 40 kilograms is standing in an elevator. The force felt by the feet of the boy will be greatest when the elevator $\left(\mathrm{g}=9.8\text{ metres }/{\sec }^2\right)$

Moves downward at a constant velocity of 4 metres/sec 

Accelerates downward with an acceleration equal to $4\text{ metres }/{\sec }^2$

Accelerates upward with an acceleration equal to $4\text{ metres }/{\sec }^2$

Stands still