A

Impulse is defined as the change in momentum of an object when a force is applied over a period of time. Mathematically, impulse (J) can be expressed as:
J = F \Delta t
where J is the impulse, F is the applied force, and \Delta t is the time duration over which the force acts.
Impulse has both magnitude and direction, and it's considered instantaneous when the time interval approaches zero.
Therefore, impulse measured at an instant refers to the instantaneous effect of force applied at that specific moment.