If an object's mass is decreasing while a constant force is applied to the object, would its acceleration decrease, increase, or remain the same?

With the decreasing object mass, the acceleration will also decrease.

Explanation:

Newton's second law of motion infers the relation between force F, acceleration a and mass m of a body. It is expressed as:

F = ma

When force is constant, we get m α 1/a, that is mass is inversely proportional to the acceleration of the body.

Hence when object's mass decreases, the acceleration will increase. and vice versa