Basketball players.
cagers
Generally speaking, no. The rules change a little from place to place, but in most professional basketball leagues all players on the court can call a time-out if theur team is in posetion of the ball.
refery will call travel
A basketball court.
to keep the players safe, call fouls, and keep the game fair
Coaches, players, and referees.
Yes, the assistant can call a timeout, players on the court can also call timeouts.
The referee would usually call a jump ball. If one of the players was too aggressive, he/she may also call a foul on that player.
The officials call a violation, and possession is handed over to the opposing team.
They call it basketball as well.
Streetball as it pertains to basketball does not have official rules. Usually players on offense will call fouls on the defense although defensive players may admit when they have fouled.