Question

what observation made fleming investigate the mold on the plate?
far fewer bacterial colonies were growing near the mold on the plate.
the mold growing near the bacterial colonies grew much better than the other mold on the plate.
mold growing near the bacterial colonies died.
more bacterial colonies were growing near the mold.
the mold turned a different color when it was growing near the bacterial colonies.

Explanation:

Alexander Fleming observed that the area around the Penicillium mold on his bacterial culture plate had significantly fewer bacterial colonies, indicating the mold produced a substance inhibiting bacterial growth. This observation led to the discovery of penicillin.

Answer:

Far fewer bacterial colonies were growing near the mold on the plate.