Which sentence states a fact?
A: Serena Williams was too young when she started playing tennis.
B: Serena Williams began playing tennis when she was four years old.
The second sentence states a fact.
Serena Williams began playing tennis when she was four years old.
It can be proved by reading a book or an article about Serena Williams.
The first sentence states an opinion.
Serena Williams was too young when she started playing tennis.
Too young shows what a person believes, thinks, or feels. Another person might have a different opinion about how young is too young.