Joe wanted to experiment with different factors that affect the freezing rate of water. he put two cups of water into each of two identical glass bowls. next, he stirred sugar into the water in one of the bowls, and he put both bowls in the freezer. he checked their temperatures after one hour, and measured how much water was still liquid in each bowl. what was the variable that changed in this experiment? a. the amount of time each bowl was left in the freezer b. the amount of sugar mixed into each bowl c. the size and shape of each bowl d. the amount of water each bowl contained