20. Which of the following statements is correct? (A). The system does work on the surroundings when an ideal gas expands against a constant external pressure. (B). The internal energy of a system increases when more work is done by the system than heat is flowing into the system. (C). The internal energy of a system decreases when work is done on the system and heat is flowing into the system. (D). All the statements are true. (E). All the statements are false.