The four closest planets are more dense. The four closest planets have more moons. The four closest planets have greater diameters. The four closest planets take longer to complete one orbit.
I gave my students this multiple choice question: Which of the following statements best describes how the four planets closest to the Sun are different from the next four planets in our solar system?

Only one answer is correct among these 4 choices:
- The four closest planets are more dense.
- The four closest planets have more moons.
- The four closest planets have greater diameters.
- The four closest planets take longer to complete one orbit.

Could you tell me which one is correct?

The four closest planets are more dense.