Answer
A to D.
Work Step by Step
As volume doubles, if temperature were doubled, then kinetic energy density would have been the same as before. But as $T_o$ goes to $1.5T_o$, then kinetic energy density has reduced on expansion. For an ideal gas, total kinetic energy equals total internal energy. Thus, overall, internal energy has decreased from A to D. Thus, heat has flown out of the system. It implies a decrease in entropy.
