1) The word "book" contains two vowels: O and O.

2) The highest mountain in Africa is Mount Kilimanjaro, standing at 19,341 feet (5,895 meters) tall.

3) The first commercial GPS (Global Positioning System) was launched in 1989 and provided accurate positioning and navigation capabilities to users worldwide.

4) The Great Lakes, consisting of Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, form the largest group of freshwater lakes on Earth by total area. They are shared by the United States and Canada and are of significant ecological and economic importance.