10. A piston system containing 1 mole of ideal gas in a 10 liter volume initially. The system is put in thermal contact with the environment at 20℃ and 1 atm of pressure. The piston is then released and the volume expands slowly in a quasi-static manner. The temperature is maintained at 20℃ during the whole process. The expansion stops when the pressure inside the piston reaches 1 atm. What is the volume of the gas chamber after the expansion? (The universal ideal gas constant, R, is 0.082 Liter-atm/K/mole.)
(A) 24.1 liter；
(B) 22.1 liter；
(C)18.4 liter；
(D) 16.9 liter；
(E) 12.3 liter.