Consider an ecosystem consisting of a prey and a predator. If H is the density of prey, P is the density of predator, r is the intrinsic rate of prey population enhance and q is the predation rate coefficient, which of the following correctly shows change in prey population density with time?
a. dH/dT = rH + qP
b. dH/dT = rH - qHP
c. dH/dT = qH - rHP
d. dH/dT = qH + rHP