Which one of the following is a second order reaction?

The rate of a certain reaction depends on concentration according to the equation $\frac{-dc}{dt} = \frac{K_1 C}{1 + K_2 C}$. What is the order of the reaction when the concentration $(C)$ is very high?

For a reaction of order $n$,the unit of the rate constant is :

Differential form of the rate equation is $\frac{dx}{dt} = k[P][Q]^{0.5}[R]^{0.5}$. Which statement about the above equation is wrong?

The rate law for the reaction $A + B \rightarrow P$ is given by $\text{rate} = k[A]^2[B]$. The rate constant of the reaction at $300 \text{ K}$ is $6.0 \text{ M}^{-2} \text{s}^{-1}$. Calculate the rate of the reaction when $[A] = 1 \text{ M}$ and $[B] = 0.2 \text{ M}$. (in $\text{ M s}^{-1}$)

For a zero order reaction,will the molecularity be equal to zero? Explain.