Amaranda and Bartolo Consume Only Two Goods, X and Y

Amaranda and Bartolo consume only two goods, X and Y. They can trade only with each other and there is no production. The total endowment of good X equals the total endowment of good Y. Amaranda's utility function is U(x_A, y_A) = min{x_A, y_A} and Bartolo's utility function is U(x_B, y_B) = max{x_B, y_B}. In an Edgeworth box for Amaranda and Bartolo, the set of Pareto optimal allocations is

A) the main diagonal.
B) both diagonals.
C) the whole Edgeworth box.
D) the edges of the box and the main diagonal.
E) the edges of the box.