Explanation
Correct answer: D.
Choice D is the best answer because it most accurately states the main purpose of the text. The text first states that animals make use of objects as tools to help them achieve different goals. The text then explains that although people used to think only primates use tools, tool use by dolphins (aquatic mammals) and palm cockatoos (birds) has shown that primates are not the only animals that use tools. Thus, the main purpose of the text is to argue that a variety of animals, not just primates, use tools.
Why the other choices are wrong
Choice A
Choice A is incorrect because the text doesn’t mention intelligence at all, focusing just on the idea that animals use tools. Further, the text mentions one kind of bird (palm cockatoos) only as an example of a non-primate that uses tools and describes its use of tools as creative, not unintelligent.
Choice B
Choice B is incorrect. Although the text mentions tool use in primates (a group that includes humans) and in palm cockatoos, it doesn’t compare humans’ tool use with palm cockatoos’ tool use. The text mentions palm cockatoos only as one example out of the variety of animals that use tools and never directly mentions tool use in humans.
Choice C
Choice C is incorrect because the text discusses tool use but never makes any mention of intelligence. Rather than establishing that tool use doesn’t indicate intelligence, the text describes certain tool use as inventive and creative.