The correct answer is A. A referee.
A referee is the person who controls a football match. They are responsible for ensuring that the match is played fairly and that the rules are followed. They have the authority to award penalties, send players off, and stop the match if necessary.
An umpire is the person who controls a cricket match. They are responsible for ensuring that the match is played fairly and that the rules are followed. They have the authority to award runs, dismiss batsmen, and stop the match if necessary.
A spectator is a person who watches a sporting event. They do not have any authority over the event and are not allowed to interfere with the play.
A goalkeeper is a player who is responsible for preventing the other team from scoring goals. They are the only players who are allowed to use their hands inside the penalty area.