Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

The American type of football was developed in the 19th century from soccer and rugby football. Played by professionals, amateurs, college and high school students, or young children, football in American is one of the most popular sports besides basketball and baseball. It attracts millions of fans each fall and people are very supportive of their favourite teams. The football playing field of today is rectangular in shape and measures 100 yards long and 53.5 yards wide. White lines are painted on the playing field to mark off the distances to the end zone. The games isdivided intofourquarters,each fifteen minuteslong. The first two quarters are known as the first half. There is a rest period between two halves which usually last about fifteen minutes. Each team has eleven players. Each team has offensive players who play when the team haspossession of the ball and defensive players who play when the other team has the possession of the ball. Because of the body contact players have during the game, helmets are worn to protect their head and face area, whereas pads are worn to protect the shoulders, arms, and legs. Also, there are officials carrying whistles and flags to make certain that the rules of thegame are followed during the game. The football is made of leather and is brown in colour. It is shaped much like an oval and has white rings near each end of the football. These rings help the players see the ball when it is thrown or someone is running with it. The eight stitches on the top of the football help the players to grip the ball when throwing or passing. The most famous game of the year is Super Bowl that is played in January or February. It is televised around the world and is watched by millions of people each year.

What do officials do during the game of football?