A heater letting of heat is an example of release of energy. Please comment if you have any questions about my answer.<span />
Answer:
Solid
Explanation:
Diphenylamine has a melting point of 127.4 F or 53 C so at room temperature ~70 F or 21 C its a solid.
As the gas cools it condenses and becomes a liquid its atoms also become smaller
The answer is C. Hydrogen Bond