Final answer:
To double the volume of a gas, the temperature needs to double as well. Therefore, if the original temperature is 30°C, the Celsius temperature needed to double the volume of the gas would be 60°C (option b).
Step-by-step explanation:
A gas follows Charles's Law, which states that the volume of a gas is directly proportional to its temperature, as long as pressure and amount of gas remain constant.
To double the volume of a gas, the temperature needs to double as well. Therefore, if the original temperature is 30°C, the Celsius temperature needed to double the volume of the gas would be 60°C (option b).