The Figure Below Shows Arcticland's Annual Production Possibilities Boundary for the Production

The figure below shows Arcticland's annual production possibilities boundary for the production of fish and ice.
FIGURE 33- 4
-Refer to Figure 33- 4.Starting from point A and moving to point B,the opportunity cost of producing each additional tonne of ice is

A) constant.
B) decreasing followed by increasing.
C) increasing followed by decreasing.
D) increasing.
E) decreasing.