The correct option is B Mating
For any monkey to ensure its survival, it needs energy to survive and grow. Also, it should protect itself from predators and extreme calamities; and removing the unnecessary waste from the body is essential as accumulation of waste is not desired. But reproduction is not essential for the survival of the monkey but to continue their species. So, mating is not essential for the survival of monkeys but for the survival of the species of monkeys.