a) Under what circumstances would a constant force result in increasing acceleration on a body? b) Under what circumstances would a constant force result in zero acceleration on a body?

Remember the equation:

F = m*a

where F is force, m is mass and a is acceleration.

If we have F constant. and we want that increases, then we can have the case where m decreases.

The mass can decrease in cases like a rocket, where as the fuel of the rocket consumes, the mass of the rocket decreases and the acceleration increases.

b) The cases where a constant force results in a constant acceleration of zero, is when the force is canceled, an example of this is the constant force of the gravity in all the objects. The objects that are in the ground are being affected by this force, but the gravitational force is canceled with the normal force of the ground. Then we have a constant force that does not cause any acceleration.

d is the answer i came up with