1) Bats are the only mammals capable of sustained flight.

2) The ocean is home to an incredible variety of marine life, including thousands of species of fish, mammals, reptiles, and invertebrates.

3) Serena Williams, an American tennis player, has won a total of 23 Grand Slam singles titles, making her one of the most successful players in the history of the sport.

4) The concept of self-driving cars, or autonomous vehicles, is being actively developed by companies such as Tesla, Google (Waymo), and Uber.