Correct Answer  Option 4 : Ns
The correct answer is option 4) i.e. Ns
CONCEPT:

Impulse (J): The change in momentum of an object when the object is acted upon by a force for a certain amount of time is called impulse. Impulse is expressed mathematically as
Δp = FΔt
Where Δp is the change in momentum, F is force, and Δt is the time taken.
EXPLANATION:
Impulse is given by Δp = FΔt
The SI unit of force is N, and that of time is s.
 Hence, the SI unit of impulse is Ns.