Which of the following is a critical assumption in order for the mark-recapture method to be useful in generating an estimate the size of wildlife populations?

A) More individuals emigrate from, as opposed to immigrate into, a population.
B) Over 50% of the marked individuals were trapped during the recapture phase.
C) There is a 50:50 ratio of males to females in the population before and after trapping and recapture.
D) Marked individuals have the same probability of being recaptured as unmarked individuals during the recapture phase.