saac’s teacher illustrated the importance of working cooperatively on a group project by teaming up with other teachers to organize a successful fieldtrip.

Which definition best fits the meaning of the word illustrated in the sentence?

illustrate
v. \ ˈi-lə-ˌstrāt \

1. to light up or make brighter
2. to clarify something confusing
3. to make clear by serving as an example or instance
4. to provide with visual features intended to explain or decorate