NEED NOW Read the excerpt from "Marine Mammals.”

Marine mammals are classified into four different groups: cetaceans (whales, dolphins, and porpoises), pinnipeds (seals, sea lions, and walruses), sirenians (manatees and dugongs), and marine fissipeds (polar bears and sea otters).

–"Marine Mammals,"
National Oceanic and Atmospheric Administration

Why does the author use classification to help guide readers through this part of the text?

It helps the author define the term “marine mammals.”
It helps the author identify types of marine mammals.
It helps the author describe what marine mammals look like.
It helps the reader visualize the types of marine mammals.