chemicals to react. volcanoes to erupt. lightning to strike Earth. the planets to orbit the Sun.
I gave my students this multiple choice question: When Isaac Newton theorized that gravity caused objects to fall to the ground, he had also discovered the force that causes

Only one answer is correct among these 4 choices:
- chemicals to react.
- volcanoes to erupt.
- lightning to strike Earth.
- the planets to orbit the Sun.

Could you tell me which one is correct?

the planets to orbit the Sun.