Please help fast Who observed one cell dividing into two, which led to another tenet of the cell theory: cells come from preexisting cells?
A: Robert Brown
B: Matthias Schleiden
C: Theodore Schwann
D: Rudolph Virchow

Red blood cells are responsible for transporting oxygen in the blood. people with sickle cell anemia were born with a defective gene that results in sickle-shaped red blood cells. individuals with the disease often suffer pain in their extremities due to the build-up of these cells causing blockages in the blood vessels. the shape of the blood cells also reduces the amount of oxygen transported in the blood.