The contact force is indeed caused by "Contact".
Air resistance is basically a type of friction, which is apparently present providing two object contact.
The rest selections are all interaction force, which is not necessarily caused by contact.
Answer:
the formula is efficiency = output / input × 100%
Condensation happens when molecules in a gas cool down. As the molecules lose heat, they lose energy and slow down. They move closer to other gas molecules. Finally these molecules collect together to form a liquid. Hope it helps
<span>If we pollute the fresh water we have, there will be a shortage of clean drinking water in the future.</span>