#### Answer

The unit of $k$ is :
a) $s^{-1}$ - first order reaction
b) $M^{-1}s^{-1}$ - second order reaction
c) $M.s^{-1}$ - zeroth order reaction

#### Work Step by Step

We know that the unit of the rate of the reaction is $Ms^{-1}$, and the unit of $[A]$ is $M$.
In a first order reaction:
rate of reaction = $k$$[A]$
So, the unit of $k$ is : $s^{-1}$
In a second order reaction:
rate of reaction = $k$$[A]^2$
So, the unit of $k$ is : $M^{-1}s^{-1}$
In a zeroth order reaction:
rate of reaction = $k$
So, the unit of $k$ is : $Ms^{-1}$