1. Serena Williams, who started playing tennis when she was three, is one of the top tennis players today. 

2. The Great Barrier Reef, which is the world's largest coral reef. is in eastern Australia. 

3. Fur seals, for which they are hunted, almost became extinct during the 19th century. 

4. Robert Ballard, is a deep-sea explorer, who is well-known for discovering the Titanic.

5. The octopus which can change its color to hide from predators is an intelligent animal. 

1. Serena Williams, who started playing tennis when she was three, is one of the top tennis players today

2. The Great Barrier Reef, which is the world's largest coral reef, is in eastern Austrailia

3. Fur seals, which are hunted for their fur, almost became extinct during the 19th century

4. Robert Ballard, who is a deep-sea explorer, is well-know for discovering the Titanic

5. The octopus is an intelligent animal which can change its color to hide from predators.