In which of these situations do the quantities combine to make 0?
A. A player in a game earns 4 points for getting an answer right. She
then earns 4 points for making it around the board.
B. A bird flies 25 feet up in the air. It then flies 25 feet across to its
nest.
C. A car is filled with 10 gallons of gas. Half of the 10 gallons are
then used on a day's drive.
D. Veronica receives $21 for babysitting. She then spends $21 on a
new shirt