One of the most important principles in biology is that all living things must come
from other living things. This principle was not discovered until the eighteenth
century. Before that, people believed that life could come from nonliving matter. For
example, they thought that worms could come from meat. Then an Italian scientist
named Francesco Redi tried an experiment. He covered some meat with a cloth so that
flies could not land on it. When no worms grew on the meat, he knew that the worms
really came from
a. scientists.
b. the cloth.
c. fly eggs.
d. the meat