-Robinson Crusoe Divides His Time Between Catching Fish and Gathering

-Robinson Crusoe divides his time between catching fish and gathering fruit.Part of his production possibilities frontier is given in the above table.Mr.Crusoe,while lonesome,is efficient and always stays on his PPF.Mr.Crusoe is consuming 20 kilograms of fish.Then he decides to slowly become a vegetarian and decreases his consumption of fish to 9 kilograms.This decision means that Mr.Crusoe will

A) be able to enjoy a gain of 9 kilograms of fruit.
B) incur an opportunity cost of 9 kilograms of fruit.
C) incur an opportunity cost of 99 kilograms of fruit.
D) incur an opportunity cost of 20 kilograms of fish.
E) incur an opportunity cost of 9 kilograms of fish.