Which best describes organisms of the Precambrian era?

A. land plants and animals

B. dinosaurs and primitive mammals

C. single-celled organisms and soft, boneless animals

D. ferns and flying reptiles

Out of the choices given, the best way to describe the organisms of the Precambrian era are they were single-celled organisms and soft, boneless animals. One thing from that time that we still have today is the jellyfish. The correct answer is C.