Answer:
A. 49 joules
Step By Step Solution:
Via kinematic equations we can must first determine the velocity of this object after 10 meters (since halfway of 20 meters is 10).

Where the initial velocity is zero since it's held at a height of 20 meters, hence it's not moving initially, g is the average gravity on Earth 9.8 m/s^2 and d is the distance this object will travel so 10 meters. By plugging these values in we obtain:

And the equation for kinetic energy is :

So the kinetic energy halfway after being released is 49 joules.
As we know from the Newton's II law we can say

here if force is unbalanced then it is for sure that net force on the system is non zero
so here the object must have some acceleration here
so here we can say that object must have change in velocity due to unbalanced force present on it
now the correct option in this case must satisfy the change in velocity condition.
SO correct answers will be
<em>Decelerate. </em>
<em>Stop moving. </em>
<em>Start moving. </em>
<em>
Accelerate. </em>