Name at Least One Conservation Law That Prevents Each of the Following

Short Answer

Name at least one conservation law that prevents each of the following reactions:
a) $\pi$ ^- + p $\rightarrow$$\Sigma$ ⁺ + $\pi$$\degree$
b) p $\rightarrow$ $\pi$ ⁺ + $\pi$ ⁺ + $\pi$ ^-