If a gas is compressed isothermally, which of the following statements is true? Energy is transferred into the gas by heat. No work is done on the gas. The temperature of the gas increases. The internal energy of the gas remains constant. None of those statements are true.

The internal energy of the gas remains constant,

Explanation:

The isothermal process can be defined as a thermodynamic process in which the temperature of the system remains constant.In isothemal process the process of transfer of heat energy from the surrounding to the system or to the system from the surrounding takes place at constant temperature.

in isothermal process internal energy of the system remains unchanged or constant.

For ideal gas internal energy of the system depends on the temperature.

For ideal gas when it is compressed the work is done by the surrounding on the gas is positive and heat added to the system is negative .When the heat energy is absent,both temperature and internal energy increases. As it is a isothermal process and temperature remains constant the gas must transfer the positive amount of heat to the system.

Hence internal energy of the system of gas remains constant.