You are given a sentence and a question. You're expected to write the correct answer based on the sentence.

Sentence: A matchbox can slide across a greenhouse floor, but it doesn't move as fast as when it is slid across the backyard. Question: Which surface is the smoother one?
greenhouse floor

Sentence: A glider and a bird are both cruising through the sky at the same rate of speed. Question: If the bird gets tired and lands before the glider, which will have travelled the least distance?
bird

Sentence: Our earth is one of the largest objects in space, but nothing compared to the sun. Question: Which object has stronger gravity?

Sun