The slope of a production possibilities curve is _ because _.

The slope of a production possibilities curve is _ because _.
A.negative; producing less of one good requires producing less of the other
B.positive; producing more of one good requires producing less of the other
C.negative; producing more of one good requires producing less of the other
D.positive; producing more of one good requires producing more of the other
正确答案：negative; producing more of one good requires producing less of the other