Part 1. Definition
You are given a paragraph, a question and some answer options (associated with "A", "B", "C", "D", etc.) You need to list all the correct answer options with their associated letters (e.g. "A" can be a valid answer). Note that sometimes, more than one option can answer the question correctly and completely. In those cases, please generate all such options separated by a comma (e.g. "A, B" is a valid answer). Do not generate anything else apart from one or more of the following characters: 'A', 'B, 'C', 'D', etc.
Part 2. Example
Paragraph- Sent 1: Obama was born on August 4, 1961, at Kapiʻolani Maternity & Gynecological Hospital in Honolulu, Hawaii.
Sent 2: He is the only President to have been born in Hawaii.
Sent 3: He was born to a white mother and a black father.
Sent 4: His mother, Ann Dunham (1942-1995), was born in Wichita, Kansas, of mostly English descent, with some German, Irish, Scottish, Swiss, and Welsh ancestry. Question: How old was Obama's mother when he was born? (A) teenager (B) in his 40s (C) mid 20s (D) almost twenty.
Answer: D.
Explanation: Obama was born in 1961. His mother was born in 1942 and 1961-1942=19. Therefore, "almost twenty" answers the question sufficiently.
Part 3. Exercise
Paragraph- Sent 1: "What goes up must come down."Sent 2: You have probably heard that statement before.
Sent 3: At one time this statement was true, but no longer.
Sent 4: Since the 1960s, we have sent many spacecraft into space.
Sent 5: Some are still traveling away from Earth.
Sent 6: So it is possible to overcome gravity.
Sent 7: Do you need a giant rocket to overcome gravity?
Sent 8: No, you actually overcome gravity every day.
Sent 9: Think about when you climb a set of stairs.
Sent 10: When you do, you are overcoming gravity.
Sent 11: What if you jump on a trampoline?
Sent 12: You are overcoming gravity for a few seconds.
Sent 13: Everyone can overcome gravity.
Sent 14: You just need to apply a force larger than gravity.
Sent 15: Think about that the next time you jump into the air.
Sent 16: You are overcoming gravity for a brief second.
Sent 17: Enjoy it while it lasts.
Sent 18: Eventually, gravity will win the battle. 
Question: How can humans overcome gravity? (A) Humans can climb a set of stairs or jump on a trampoline (B) It is impossible (C) Climbing stairs (D) Magic (E) Apply force larger than gravity (F) Jumping (G) You can't (H) Traveling to Earth (I) Have a giant rocket.
Answer:
A, C, E, F.