(a) An ideal gas is expanded slowly and isothermally. Does its entropy increase, decrease, or stay the same?

(b) Choose the best explanation from among the following:

I. Heat must be added to the gas to maintain a constant temperature, and this increases the entropy of the gas.

II. The temperature of the gas remains constant, which means its entropy also remains constant.

III. As the gas is expanded its temperature and entropy will decrease.