Nhận biết (M1)

A study of a remote, predator-free island found that its bird species had, over many generations, evolved progressively weaker wings, and several had lost the capacity for flight altogether. Because the island had no native predators from which the birds would need to flee, researchers proposed that maintaining the muscles and metabolism required for flight is biologically costly and that, where flight confers little survival advantage, ______.

Which choice most logically completes the text?

• A.

  birds will retain the ability to fly regardless of their surroundings.

• B.

  natural selection may favor individuals that invest fewer resources in flight.

• C.

  predators are almost certain to be reintroduced over time.

• D.

  birds tend to migrate toward islands that contain more predators.