Answer:
1. At 9:10 this morning, we'll be leaving for the natural history museum.
2. Please bring the following materials with you: pencils, paper, erasers, and a notebook.
3. The bus will be back at 4 AM to pick us up.
4. The special exhibit on birds contains the following types: prehistoric birds, seabirds, and domestic birds.
5. The letter we wrote to the museum began: "Dear Sir, Please let us known when the special exhibition on penguins will be shown at your museum."
Step-by-step explanation:
When related to time, as in sentence 1, colons are used between hours and minutes. When only hours are used, a colon is not needed, as in sentence 3, unless you want to emphasize 4:00 AM exactly.
Colons are also used preceding a list. This is the case in sentences 2 and 4.
Colons can further be used to quote something; this is the case in sentence 5.