In sperm competition, what is 'second-male advantage'?
a. The observation that when females mate with two males, each male fertilizes the same number of eggs
b. The observation that when females mate with two males, the second male fertilizes most of the eggs
c. The observation that females routinely mate with at least two males before laying eggs or becoming pregnant
d. The observation that accessory fluids prevent matings by second males—for example, by forming copulatory plugs