At least 3, sometimes more depending on location
3 referees are in soccer and football
depends on what country he referees in
They are technically called assistant referees.
Soccer referees are graded by levels, not by classes. Informally, a referee might be considered "Class A" if they are certified International referees.
It matters if it's professional. If not, there can be a few as 1. If professional, there are 2-3 referees.
Cristiano Ronaldo wears 17 when he plays for Portugal.
If you're talking about soccer referees, I don not believe so.
red or yellow