In which of these situations do the quantities combine to make 0?
A. A car is filled with 10 gallons of gas. Half of the 10 gallons are then used on a day's drive
B. A rock climber goes 40 feet down into a valley. She then goes 40 feet up a cliff o C. Glenn spends $8 on a tutor, and then he spends $8 on a new book
D. A player in a game earns 5 points for getting an answer right. She then earns 5 points for making it around the board
