None, there are umpires. There is always at least one who calls balls and strikes from behind home plate. Depending on the league and level of competition there can be one to three additional referees who make calls on the basepaths.
Softball doesn't have quarters. It has innings. Each inning consists of a bottom and a top. (In the top the home team is out in the field on defense and the visiting team is batting. In the bottom it's flip flopped.) Most games will last seven innings, but there is a mercy rule. If a team is up by either 15 points by the end of the third inning, or by 10 at the end of the fifth inning, (or after) the game will be called.
there are 4 bases in softball, homeplate, first base, second base, third base...
2 refs, 2 linesman
there are 4 refs for each team idiot
there are six refs in a NFL football game
there are 3 refs in a high-school football game
2000000000000 refs and 5667788880 linesman
10
Usually 3
There are three refs in an NBA game- one on the baseline, one near the sideline, and one near half-court.
the average number in the little league is two
2 refs 2 linesmen
there are 2 refs and 2 line watchers
Two halves. 20 to 40 minute a piece. Usually 25 min