Question

which sentence states a fact? hummingbirds molt, or replace old feathers with new ones, once a year. though small, hummingbirds have the most remarkable feathers of any bird.

Explanation:

A fact is a statement that can be proven. "Hummingbirds molt, or replace old feathers with new ones, once a year" is a verifiable statement. The second statement "Though small, hummingbirds have the most remarkable feathers of any bird" is an opinion as "most remarkable" is subjective.

Answer:

Hummingbirds molt, or replace old feathers with new ones, once a year.