challenge: What is distinctive about the plumage of the great elaenia's sexes?
  
  A. The males have a dark sooty brown head, while the females have a light olive-gray head.
  B. The males have a vibrant yellow crown, while the females have a dull gray crown.
  C. The females have a longer tail than the males.
  D. The sexes have the same plumage.
  Answer: 