Which of the following statements is true about certainty of paternity?

A) Young or eggs laid by a female are likely to contain the same genes as another female's eggs in a population of birds.
B) Certainty of paternity is high in most species with internal fertilization because the acts of mating and birth are separated by time.
C) Males that guard females they have mated with are certain of their paternity.
D) Certainty of paternity is low when egg laying and mating occur together, as in external fertilization.
E) Paternal behavior exists because it has been reinforced over generations by natural selection.