7. What is the entropy change when 2.0 moles of argon in a container of volume 500 cm3 is allowed to expand isothermally to 1000 cm3 at 25oC？ (A)5.7 J/K　(B)11.5 J/K　(C)- 5.7 J/K　(D)- 11.5 J/K