A scientist conducted an experiment to determine if temperature affects the length of a butterfly's life cycle. She collected several eggs that were laid at the same time by one butterfly, and divided them into three aquariums. Each aquarium contained enough food and water for all of their lifetimes. The containers were kept at 60º F, 70º F, and 80º F.
What is the tested or manipulated variable?
A. the temperature of each aquarium
B. the number of days it took for adult butterflies to appear in each aquarium
C. the number of eggs that hatched in each aquarium
D. the total number of days in each butterfly's life cycle