What Is Meant by the Human Carrying Capacity of the Earth

What is meant by the human carrying capacity of the earth?

A) the number of tons of edible food that can be produced by all of the earth's cultivable land
B) the maximum number of people that the earth can support over time
C) the amount of oxygen consumed by all living organisms in relation to the amount of oxygen produced by all living plants
D) the total weight of all living organisms in relation to the weight of all non-living material including the earth's water mass