Options:
A). fungi.
B). cells.
C). mildew.
D). gasoline.
E). fungus.
F). matter.
G). telescopes.
H). sunlight.

Fact 1: Cells vary in size as well as shape, but all cells are very small. Fact 2: An embryo is so small that it requires a microscope in order to be seen. Given the two facts above, what requires a microscope in order to be seen?
Answer:
B).