Which sentence states a fact?
A: Though small, hummingbirds have the most remarkable feathers of any bird.
B: Hummingbirds molt, or replace old feathers with new ones, once a year.
The second sentence states a fact.
Hummingbirds molt, or replace old feathers with new ones, once a year.
It can be proved by reading a book about hummingbirds.
The first sentence states an opinion.
Though small, hummingbirds have the most remarkable feathers of any bird.
Most remarkable shows what a person believes, thinks, or feels. Another person might have a different opinion about which birds have the most remarkable feathers.