Question: What is the main postulate of general relativity?

Options:

1. Gravity is a force between masses.
2. Mass warps spacetime, causing gravity.
3. Time is the same for all observers.
4. Light cannot escape from a black hole.

Correct Answer: Mass warps spacetime, causing gravity.

Solution:

General relativity posits that gravity is not a force but a curvature of spacetime caused by mass.