Answer the following question given this paragraph: 

The partial geologic time scale in Figure below shows when some of the major events in animal evolution took place. The oldest animal fossils are about 630 million years old, so presumably animals evolved around that time or somewhat earlier. The earliest animals were aquatic invertebrates. The first vertebrates evolved around 550 million years ago. By 500 million years ago, most modern phyla of animals had evolved. The first terrestrial animals evolved about 50 million years after that.


Q: The earliest animals were which kind of invertebrates?

 Choices:

- insects

- mammals

- dinosaurs

- aquatic

A:
aquatic
