Which of the following is the SI unit of Impulse ?

Impulse is defined as the product of the average force applied to an object and the time duration for which it acts.
$$\text{Impulse}=\text{Force}\times \Delta t$$

The SI unit of force is Newton ($\text{N}$) and time is second ($\text{s}$), making the SI unit of impulse Newton-second ($\text{Ns}$).