A group of student researchers is working in a wilderness area. Three of them - Pierce, Naomi, and Ikenna -come down with an unidentified illness. There are some typical causes of illness in situations like these: eating contaminated food, drinking impure water, insect bites, etc. The researchers compare what they've consumed, where they've been, what's bitten them, etc. in order to identify the cause of the illness.

All of the researchers have eaten all the same food, but not all of them got sick; so the food probably was not contaminated. Also, everyone has consumed some potentially-contaminated water. The day before the illness started, the team had been moving back and forth between Zone A and Zone B. Ikenna drank water from a natural source in Zone B and remembered getting bug bites in both Zones A and B. Gustavo only drank water from Zone A, but didn't get any bug bites because he wore bug repellent. Yukionly drank water from Zone B, but only gotbug bites in Zone A. Pierce and Naomidrank water from both zonesand got bug bites in both zones.

a) Based on this information, complete the following presence table.

	Contaminated Food	Zone A: Water	Zone B: Bug Bites	Zone B: Water	Zone B: Bug Bites	Unidentified Illness
Gustavo
Ikenna
Naomi
Pierce
Yuki

b) What is the cause of the unidentified illness?

c) Which of Mill's methods did you use to determine the cause?