Somebody start a conversation..no dry talk

Which of the following identifies a main culprit for america’s increasing weight gain

Christopher came down with chicken pox after spending time in his child’s day care. the chicken pox represents what link in the chain of transmission in this scenario?

What should be changed to make the following sentence true? "the stress model suggests that people with a predisposition for a disorder are more likely to develop the disorder when faced with stress."