Answer:
Trail 3
Explanation:
As we know by Newton's II law that rate of change in momentum is always net force applied on the object.
Here we know that

now we also know that change in momentum is known as impulse
so here impulse and force relation is given as

so here in order to find the greatest impulse we need to find the product of force and time to be the maximum as per above formula
so we have
trail 1
impulse = 500 (0.25) = 125 Ns
trial 2
impulse = 500(0.15) = 75 Ns
trial 3
impulse = 500(0.45) = 225 Ns
trial 4
impulse = 500(0.33) = 165 Ns
so out of the four trials maximum impulse is for trial 3