In 1862, a French chemist named Louis Pasteur performed the following experiment. Pasteur placed broth in a special type of flask that allowed air to enter and exit. Then, he heated the broth and flask, so they no longer contained any bacterial cells. Finally, after observing the flask for a few days and noticing that nothing grew in the flask, he was able to conclude that
A.
all cells must come from pre-existing cells.
B.
cells are spontaneously created from nonliving matter.
C.
only air is required to generate new cells.
D.
bacteria are not living organisms.