If a Brother and Sister Return Home from Trick-Or-Treating on Christmas

Multiple Choice

If a brother and sister return home from trick-or-treating on Christmas and engage in a series of voluntary trades of candy, we can conclude that:

A) the initial allocation of candy between them was distributively inefficient.
B) the initial allocation of candy between them was distributively efficient.
C) their preferences must be different.
D) the candy they collected around the neighborhood must have been different.