Several local universities hire a polling company to study how widespread cheating is in online courses. For each of the challenges listed below that this company faces, fill in the blank with the number matching the type of bias this challenge would make us worry about the most. Each type of bias will be used exactly once.

(a) Students don't want to admit that they cheat and might lie about it. _________

(b) The company doesn't have contact information for all students. _________

(c) The survey the company will administer is optional. _________

Options:

1 - Selection bias

2 - Non-response bias

3 - Response bias