The Diagram Below Shows Robinson Crusoe's Annual Production Possibilities Boundary

The diagram below shows Robinson Crusoe's annual production possibilities boundary for the production of bananas and coconuts.
FIGURE 33- 3
-Refer to Figure 33- 3. Starting from point A and moving to point B, Robinson Crusoe's opportunity cost of producing each additional kilogram of coconuts is

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