Answer the following question given this paragraph: 

The first period of the Paleozoic Era was the Cambrian. By the beginning of the Paleozoic, organisms evolved shells. Shells could hold their soft tissues together. Shells could protect them from predators and from drying out. Some organisms evolved external skeletons. These are called exoskeletons . Organisms with hard parts also make good fossils. Fossils from the Cambrian are much more abundant than fossils from the Precambrian.


Q: The first period of the paleozoic era was called what?

 Choices:

- carboniferous

- permian

- ordovician

- cambrian

A:
cambrian
