1) The word "mountain" contains three vowels: O, U, and A.

2) Serena Williams is an American professional tennis player widely regarded as one of the greatest athletes in the sport. She has won numerous Grand Slam titles and Olympic gold medals and has become an influential figure both on and off the tennis court.

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

4) The Brexit process, initiated by the United Kingdom's referendum in 2016, led to the country's withdrawal from the European Union in 2020, marking a significant political and economic change for both the UK and the EU.