question: Write a question you would see in a school textbook.
answer: When a dog smells food and begins drooling, it is responding to an external stimulus. Which of these describes a response to an internal stimulus?

question: Write a question you would see in a school textbook.
answer: What causes the blue color of the sky?

question: Write a question you would see in a school textbook.
answer:
DNA molecules contain the genetic information that determines the characteristics of a living organism. How do DNA molecules express the genetic information they contain?