What is the unit of rate constant for the zero order reaction?

What is the correct relation between rate constant and half-life for a zero order reaction?

For a zero-order reaction with rate constant $k$,the slope of the plot of reactant concentration against time is

For a zero order reaction,the plot of concentration $(a-x)$ $Vs$ time is linear with

For a reaction $A \rightarrow$ products,the half-life period is $1 \ h$. The initial concentration of reactant $A$ is $2 \ M$. If this reaction is of zero order,how many hours will it take for the concentration of the reactant to decrease from $0.5 \ M$ to $0.25 \ M$?

$A$ zero-order reaction,$A \rightarrow \text{Product}$,with an initial concentration $[A]_0$ has a half-life of $0.2 \ s$. If one starts with the concentration $2[A]_0$,then the half-life is $.... \ s$