Based on the information present in the given passage, you need to write a correct answer to the given question. A correct answer is one that correctly and completely answers the question. Do not write answers that address the question partially or incorrectly. The correct answer must be contained in the given paragraph.
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?
Example solution: 19.
Example explanation: Obama was born in 1961. His mother was born in 1942 and 1961-1942=19. Therefore, any of the following responses are considred correct: '19' and 'almost twenty'.

Problem: Paragraph- Sent 1: When you get sick, your body springs to action.
Sent 2: Your body starts to fight the illness.
Sent 3: Thats why you want to eat right and get plenty of sleep.
Sent 4: You need a strong immune system to fight off illness.
Sent 5: Plants dont have an immune system.
Sent 6: That does not mean they do not get sick.
Sent 7: Plants are affected by disease just like us.
Sent 8: Typically, their first line of defense is the death of part of the plant.
Sent 9: This prevents the infection from spreading.
Sent 10: Many plants also produce special chemicals to fight disease.
Sent 11: For example, willow trees produce a chemical to kill the bacteria.
Sent 12: The same compound is used in many acne products.
Sent 13: You can see a picture of a willow tree in Figure Plants may be smarter than we think.
Sent 14: No, they cannot talk to each other.
Sent 15: They may be able to send messages, though. 
Question: Why does part of a plant die when a plant is infected by disease?.

Solution: To fight the infection.