Which of the Following Is a Fitness Trade- Off

Which of the following is a fitness trade- off?

A) The largest male elephant seals are able to mate with many females, but smaller males rarely have the opportunity to mate.
B) Algal genotypes that can grow fast in nitrogen- limited environments are easier for predators to digest.
C) In some hornbill species, the male helps seal the female in a tree with her nest until the young are ready to fledge.
D) Moths are the best pollinators for datura flowers, but bees are the best pollinators for orchids.