There are two choices at this time: run away or fight.
I bought a lot of meat at the store: bacon, turkey, chicken, and tuna.
A dolphin is not a fish: it is a mammal.
She grabbed the microphone and asked: "Is there a doctor in the house?"
For these sentences, the colons are used to introduce lists, to emphasize the previous sentence, and to introduce dialogue. There are other uses as well, but these are the uses that apply to this assignment.