An ideal gas undergoes an isothermal compression. Which of the following statements about the internal energy of the gas is correct?

For an ideal gas, the internal energy depends only on temperature (kinetic theory). In an isothermal process, the temperature remains constant; therefore, the internal energy does not change. Although work is done on the gas during compression, an equal amount of heat is released to the surroundings to maintain constant temperature, keeping the internal energy unchanged. Options A and D describe partial truths but draw wrong conclusions about internal energy.