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.
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.
Example solution: D.
Example explanation: Obama was born in 1961. His mother was born in 1942 and 1961-1942=19. Therefore, "almost twenty" answers the question sufficiently.

Problem: Paragraph- Sent 1: Plants also detect the daily cycle of light and darkness.
Sent 2: Do you know how plants respond to these changes?
Sent 3: Some plants open their leaves during the day.
Sent 4: It is during these hours the plant can collect sunlight.
Sent 5: At night, the plant closes its leaves to prevent water loss.
Sent 6: Many plants respond to the change in the length of the day.
Sent 7: As days grow shorter, some plants respond by going dormant.
Sent 8: Dormant is when a plant suspends its growth.
Sent 9: It does this in order to survive.
Sent 10: Shorter days signal the coming of winter.
Sent 11: Winter in most areas means extreme cold.
Sent 12: It is also very dry in the winter months.
Sent 13: As winter approaches, some plants respond by their leaves changing color.
Sent 14: After the change in color, they fall off.
Sent 15: This dormancy period helps trees.
Sent 16: It allows them to survive the cold and dry winter.
Sent 17: Plants only want to grow when conditions are right. 
Question: Why do plants open their leaves during the day? (A) To collect more sunlight (B) So they can dry themselves (C) They detect daylight and open their leaves in order to collect sunlight (D) To collect water (E) So they can get as much sunlight as possible.

Solution: A, C, E.