Read the passage. If we assign the same causes to the same effects, then we should assume that if rain falls to the ground because of gravity in China, it should do the same in Japan and India. Likewise, we can assume that rain will fall to the ground in all other countries in Asia and on all other continents in the world.

What is the central idea of the passage?

Rain is heavy, so it falls to the ground everywhere.
Rain falls to the ground faster in Asian countries because of gravity.
Rain falls everywhere on the Earth because of the same cause.
Rain has different causes and effects based on the country in which it falls.