Question

study this image of a geologic time scale. how long ago did invertebrates become common on earth? 1.6 million years ago 132 million years ago 410 million years ago 520 million years ago

Explanation:

By referring to the key - events column in the geologic time - scale table, it is shown that invertebrates became common during the Ordovician period which started about 520 million years ago.

Answer:

520 million years ago