The right answer is A. Wearing safety glasses.
When practicing mountain biking, there are essentially two prevention methods: *active safety (careful driving, maintenance of equipment, etc.) for which you are an actor / actress and *passive safety (pilot protection, night lighting ...).
The cycling glasses are an essential equipment in the panoply of a cyclist. This equipment will protect you from the sun but also dust, insects and splashing water or mud.
The choice of glasses is very important because they must play their main role, protection, but must be comfortable.