Stromatolites were formed by ____.

A) animals
B) heterotrophic bacteria
C) photosynthetic bacteria
D) red alga
E) plants

Stromatolites

Layered structures formed by the growth of microorganisms in shallow water, representing some of the oldest fossils, dating back to over 3.5 billion years ago.

Photosynthetic Bacteria

Bacteria that are capable of photosynthesis, a process that converts light energy into chemical energy, often playing a key role in various ecosystems by producing organic compounds.