The net force acting on an stationary object is zero. which best describes the object’s velocity? a. the velocity is zero. b. the velocity is decreasing. c. the velocity is increasing. d. the velocity is constant, but not zero.

If the net force acting on any object is zero, then the object's acceleration
is zero.  That means that the object is not speeding up or slowing down,
and the direction of its motion isn't changing.  This is another way of saying
that its velocity is constant.

Now, if the object started out stationary as the question says, and the
net force on it is zero, then it can't get going, and it remains stationary.
The acceleration is zero, and so is the velocity. (choice-A)

You get 6 for mechanical