The given graph is a representation of kinetics of a reaction. The $y$ and $x$ axes for zero and first order reactions, respectively are:

1. A
   zero order ($y=\text{concentration}$ and $x=\text{time}$), first order ($y=t_{1/2}$, and $x=\text{concentration}$)
2. B
   zero order ($y=\text{concentration}$ and $x=\text{time}$), first order ($y=\text{rate constant}$ and $x=\text{concentration}$)
3. C
   zero order ($y=\text{rate}$ and $x=\text{concentration}$), first order ($y=t_{1/2}$ and $x=\text{concentration}$)
4. D
   zero order ($y=\text{rate}$ and $x=\text{concentration}$), first order ($y=\text{rate}$ and $x=t_{1/2}$)