As altitude increases, the pressure decreases. The decrease in pressure lowers the boiling point of water, which causes water to boil quicker at higher altitudes. Consider the following variables.
A: altitude
P: pressure
B: boiling point of water
T: time taken to boil water
Between which of the following pairs of variables does a positive covariant exist?
A. A and P
B. A and B
C. A and T
D. P and B