Typically the queen honeybee is mother to all the bees in a hive; after mating with several male drones from other colonies, she lays fertilized eggs that develop into all-female worker bees and lays unfertilized eggs that become all-male drones. When a queen dies, workers often lay unfertilized eggs that hatch into drones. Yet workers rarely reproduce while a queen reigns.
According to natural selection (natural selection: n.[生]自然选择,物竞天择说) theory, a worker would enhance her fitness—or ability to propagate her genes—by hatching her own eggs in addition to or in place of the queen’s. But a typical worker’s fitness would be diminished if other workers’ sons, who have less genetic material in common with the worker, supplanted the queen’s sons (the worker’s brothers). Researchers, testing the hypothesis that workers usually somehow block each other’s attempts to reproduce, put unfertilized eggs laid by workers and by the queen into a hive. Other workers quickly devoured the workers’ eggs while leaving the queen’s eggs alone.
17. The author refers to the experiment described in lines 16-19 in order to
(A) explain how worker bees are prevented from mating with drones
(B) explain how worker bees hatch and nurture the queen’s young
(C) demonstrate the universality of natural selection
(D) show that worker bees are capable of thwarting each other’s attempts to reproduce（D）
(E) provide a model of daily life in a typical honeybee hive
18. The inner workings in a honeybee hive that regulate reproduction, as they are described in the passage, are most similar to which of the following types of human societies?
(A) A totalitarian society in which citizens’ “policing” of each other’s actions helps to maintain the status quo.
(B) A pacifist state in which the individuals are strongly opposed to the use of violence or aggression to settle disputes.
(C) A democratic society in which the voice of the majority rules.
(D) A parliamentary society in which a few members, organized as a cabinet wield executive power.（A）
(E) An anarchic state in which order and stable social structures are lacking.
19. The passage best supports which of the following inferences about the fitness of honeybees?
(A) Reproduction diminishes any individual honeybee’s fitness.
(B) An individual worker’s fitness can be maintained without the individual herself reproducing.
(C) A hierarchy of stronger and weaker individuals among the worker bees determines which individuals will reproduce when a queen dies.
(D) While a queen reigns, the fitness of the worker bees is increased and that of the drones is diminished.（B）
(E) Fitness encourages worker bees to hatch honeybee eggs without regard for the relatedness of the young to the “parent.”
20. The passage suggests which of the following about the eggs laid by worker bees?
(A) One of the eggs hatches into the next queen.
(B) The eggs are invariably destroyed by other worker bees.
(C) Each worker tries to hide her eggs from the other worker bees.
(D) The eggs hatch only if the worker has mated with a drone from another hive.（E）
(E) The eggs are less likely to be harmed by other workers if the queen is dead.