Final answer:
The correct answer is (c) Heat is released, work is done on the gas; when a gas cools, it releases heat, and when it is compressed, work is done on it.
Step-by-step explanation:
The signs for heat and work for a gas that cools and is being compressed can be determined based on thermodynamic conventions. When a gas cools, it typically releases heat to the surrounding environment; hence, the sign for heat would be negative as the system loses heat. Conversely, when a gas is compressed, work is done on the gas, meaning an external force is applied to decrease the gas volume, and thus, the sign for work is also negative in this context according to the convention. Therefore, the correct answer to the student's question is (c) Heat is released, work is done on the gas.