Answer:
the curved path of a celestial object or spacecraft around a star, planet, or moon, especially a periodic elliptical revolution.
Answer:
D. Graduating from college
Answer:
The answer is C: To add supplemental information that explains the situation.
Explanation: In the passage from "When Birds Get Flu", the author mentions about the study made by Dr. Dowell and his concern with avian infuenza. The author explains that this is a bird flu, what birds (poultry) this virus usually strikes and also informs that it is rare for humans to get sick because of the bird flu.