Long ago, it was believed that maggots came from meat. In the late 1600s, Francesco Redi hypothesized that maggots came from flies rather than from meat. Which of these experimental designs could be used to test Redi's hypothesis?

A.) an experiment using covered, unrefrigerated meat
B.) an experiment using uncovered, unrefrigerated meat
C.) an experiment using flies under a bell jar
D.) both A and B