How did the development of a porcelain filter, called the Chamberland-Pasteur filter, help scientists discover viruses?
a. After filtering a liquid plant extract, the scientists could see the virions using the light microscope.
b. After filtering a liquid plant extract, the disease was still transferred to a healthy plant.
c. After filtering a liquid plant extract, the virus cells multiplied.
d. After filtering a liquid plant extract, scientists were able to trace historical footprints.