In mexico, cinco de mayo has been celebrated with
a. decoration of trees.
b. a formal dinner with the mayor.
c. parades and re-ennactments.

The correct Answer is C. although this is really the case for Puebla (city) mostly. The rest of Mexico does not have extended celebrations, although the schools are closed, and some of the offices as well.
In Puebla, where the event originally happened, there is a major parade, and re-enactment.