Fill in the blank (_) in the following sentence from the following choices.
Sentence: The structure that Adam was in was more unstable than that of Aaron's because _ was in an ancient building.

Choice 1: The structure that Adam was in was more unstable than that of Aaron's because Adam was in an ancient building.
Choice 2: The structure that Adam was in was more unstable than that of Aaron's because Aaron was in an ancient building.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
1
1.