Which sentence states a fact?
Five South American countries border Peru: Bolivia, Brazil, Chile, Colombia, and Ecuador. Of the five South American countries that border Peru, Brazil is the most important.
A fact is something that can be proved to be true. Facts can be proved by observing, measuring, or studying information.
The flag of the United States has 13 stripes.
This is a fact. It can be proved by looking at the flag and counting the number of stripes.
An opinion is something that a person believes, thinks, or feels. An opinion cannot be proved true.
The flag of the United States is easy to draw.
This is an opinion. People may have different opinions about what makes a flag "easy" to draw.
The second sentence states a fact.
Five South American countries border Peru: Bolivia, Brazil, Chile, Colombia, and Ecuador.
It can be proved by checking a map of South America.
The first sentence states an opinion.
Of the five South American countries that border Peru, Brazil is the most important.
Most important shows what a person believes, thinks, or feels. Another person might have a different opinion about what makes a country important.