Fill in the blank (_) in the following sentence from the following choices.
Sentence: The chair could sit on the floor but not on the stair because the _ is uneven.

Choice 1: The chair could sit on the floor but not on the stair because the floor is uneven.
Choice 2: The chair could sit on the floor but not on the stair because the stair is uneven.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
2
2.