Which sentence states a fact?
Building the Great Wall of China took too long. It took hundreds of years to build the Great Wall of China.
A fact is something that can be proved true by research or observation.
George Washington became president of the United States in 1789.
This statement is a fact. It can be proved by researching what year George Washington was inaugurated president.
An opinion is something that a person believes, thinks, or feels. An opinion can be supported by evidence, but it cannot be proved true.
George Washington was a better president than Thomas Jefferson.
This statement is an opinion. People can have different ideas about what makes someone a "better" president, so the statement cannot be proved.
The first sentence states a fact.
It took hundreds of years to build the Great Wall of China.
It can be proved by reading about the creation of the Great Wall.
The second sentence states an opinion.
Building the Great Wall of China took too long.
Too long shows what a person believes, thinks, or feels. Another person might have a different opinion about how long is too long.