a constant force can at on an object for diferrent lengths of time. as the length of time the force acts increases, the impulse imparted to the object

increases
decreases
remians the same

For people who are trying to get away with castle learning, the answer is increasing. F*T/m = change in momentum < denominator increases, lesser value as a result.

a constant force can act on an object for different lengths of time. as the length of time the force act increases the impulse started to the object

I suspect your teacher is wanting is increases, but she should have put a constant net force can ...

The force under my rear in this chair is constant, and acts for long periods, but it is not imparting any impulse to my mass. Why? Because the force acting is equal and opposite to my weight, so that no NET force is acting on my rear.

Increase

The impulse imparted to an object is directly proportional to the length of time a constant force acts on it. Therefore, as the length of time the force acts increases, the impulse imparted to the object also increases.

stays the same

decreases