Which of the following statements is true?

All of the sun's radiation is reflected back into space by the Earth's atmosphere.
Air is a good insulator because the molecules in gas are very far apart.
Work can only be done by potential energy.
Total mechanical energy is calculated by subtracting kinetic energy from potential energy.

Air is a good insulator because the molecules are far apart. This reduces mobility of air molecules hence conduction is difficult.

Explanation:

For other statements :

= Kinetic energy + Potential energy

Air is a good insulator because the molecules are far apart. This reduces mobility of air molecules hence conduction is difficult.

Explanation:

:p

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.