The Teacher said, "The Earth revolves around the Sun".

The teacher said that the earth revolves around the sun.

The teacher says that the earth revolves around the sun.

The teacher said that the earth is revolves around the sun.

None of these

The teacher said that the earth revolves around the sun.

In reported speech, universal truths like this one keep their present tense.

“Revolves” remains unchanged even after converting to indirect speech.