One Mole of an Ideal Gas Undergoes a Reversible Isothermal

Multiple Choice

One mole of an ideal gas undergoes a reversible isothermal expansion from a volume of 1 L to a volume of 2 L.The change in entropy of the gas in terms of the universal gas constant R is

A) R/2
B) 2R
C) R ln(2)
D) R ln(½)
E) None of these is correct.