A scientist finds the bones of a dinosaur. What could help the scientist determine the approximate age of the dinosaur bones?
A: the index fossils in the area of the bones

Which of these is the most responsible for the changes of the seasons on Earth?
A: Tilt of Earth on its axis

At science conventions, scientists present their research, and members of the audience can discuss or ask questions about the research. The main value of these science conventions is that they allow scientists to
A: exchange their ideas.

What carries oxygen throughout the body?
A:
red blood cells