Answer the following question given this paragraph: 

There are also six types of leptons, including electrons. Leptons have an electric charge of either -1 or 0. Electrons, for example, have a charge of -1. Leptons have mass, although the mass of electrons is extremely small.


Q: How many types of leptons are there?

 Choices:

- nine

- two

- twelve

- six

A:
six
