Brody studied the geologic time scale and became interested in the sorts of life that existed in each era.

He learned that scientists dated life in this era using the law of superposition and radioactive dating. Which of the following characterizes the Cambrian period? Choose the three that apply.

A. all life lived in the sea

B. invertebrates developed

C. single-celled life

D. dinosaurs flourished

E. organisms with shells and outer skeletons developed