Fill in the blank (_) in the following sentence from the following choices.
Sentence: Paul debated on building what building material brick or PVC, because the _ is smooth.

Choice 1: Paul debated on building what building material brick or PVC, because the brick is smooth.
Choice 2: Paul debated on building what building material brick or PVC, because the PVC is smooth.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
2
2.