jmc

Five steps are taken to get from $0$ to $20$. Each step is of equal size, so each step is $4$. Three steps are taken from $0$ to $y$, so $y=3\times 4=12\to \boxed{\text{C}}$. There are five steps, and y is step number three. We can get our answer by multiplying since all the steps are the same. $$20\cdot \frac{3}{5}=12$$. So, our answer is $\boxed{12}$----stjwyl