Read the excerpt from "Are Dogs Dumb?"
Chimps can use sign language to talk to their trainers. Monkeys can learn to count. A crow can figure out how to us a stick to get at that hard-to-reach grub. Chickens can learn to play checkers. Even worms can be taught to run mazes. So which animal is the smartest? You're probably thinking that chimps are smarter than chickens. And that crows are smarter than worms. And that you’re smarter than all of them.

Which best explains how the passage supports the author's purpose?

The purpose is to instruct; it provides many supporting details about the abilities of chimps.

The purpose is to entertain; it uses a humorous tone.

The purpose is to persuade; it is trying to convince us that humans are the smartest animal of all.

The purpose is to inform; it asks a question that will be answered by the text.

The text provides some details about chimps, but that is not its main purpose. Moreover, it provides this information in a humorous tone, but it is not intended to be only read for humour only. The author is not trying to convince us that humans are the smartest animals, as he gives us many examples of other animals with great cognitive capacity. The purpose of the text is to inform. It asks the question: "So which animal is the smartest?" in order to encourage us to think about it. The way the text is written indicates that the author will answer the question later on in a way that might surprise us.