Matthias Schleiden and Theodor Schwann made which contribution to science?
A. Discovered that new organisms do not spontaneously arrive in suitable conditions, but must be brought there.
B. Discovered the process plants use for energy, photosynthesis.
C. Discovered a basic principle of chemistry, that all matter is composed of atoms.
D. Discovered a basic principle of biology, that all plants and animals are made of cells.
