Answer:
D.
Step-by-step explanation:
Uriel, in his article, should include a labeled illustration of a flightless bird and a flying bird, showing the missing body part in the flightless bird.
As the writer in his article has reported that flightless birds are not able to fly because they have some missing body parts that enables a bird to fly. So, showing a labeled diagram of that body part will help the readers to understand the text more clearly.
Therefore, option D is correct.