Question

which sentence states a fact? up to twelve inches across, the wings of an atlas moth are truly marvelous. the atlas moth, an insect, is larger than some birds.

Explanation:

A fact is a statement that can be proven. "Up to twelve inches across" is a measurable and verifiable statement about the wing - span of an atlas moth. "Truly marvelous" is a subjective opinion. "Larger than some birds" is a bit vague and not as clearly verifiable as the specific measurement.

Answer:

Up to twelve inches across, the wings of an atlas moth are truly marvelous.