Medo2020

Hello all, I'm in EB2 and I work in a public university. I am filling two Forms of I-485 (one for me and the other for my spouse) concurrently with Form I-140. I'm the principal applicant and my spouse is the derivative applicant. I think both of us are exempted from filling Form I-864, am I right? In Part 8 of Form I-485 page 14 (I have to choose one to explain why I'm exempted) I am EXEMPT from filing Form I-864 because: Which one should I check, and which one should my spouse check? PLEASE HELP. Thank you!