Which describes how Ernst Ruska and Max Knoll's contributions connect to the origin of life?
a. Their theory of natural selection explained how each cell changes over time.
b. Their creation of the electron microscope was needed to visualize the nucleus and inside of cells.
c. Their emphasis on sterilizing and hand washing allowed scientists to see how life first evolved.
d. Their conclusions that spontaneous generation did not occur lead to the concept of cell theory.