B. What does this equation mean?
area x bioproductivity = biocapacity [SUPPLY]
population x consumption per person x footprint intensity = ecological footprint
the supply is how much the earth can supply us with and the demand is how much we take from the earth.

C. What is the significance of the year 1987?
that was the year that we began to take to take more from the earth than it could give us.

D. What happened on October 6, 2007?
U.S used up all of the reacorces that the earth would give us for that year.