1. A proton decays into a neutron, a positron, and a neutrino, as shown.

 $p\rightarrown+{e}^{+}+v$

It cannot decay into a neutron and a neutrino without the emission of the positron.

Which of the following conservation laws would not be conserved if it did?

1. charge

2. lepton number

3. strangeness

4. baryon number