i-864 question about PART 1

[ilovekhmer]

I'm confused about i-864 Part 1 on what to answer. We are a joint sponsor. I am the the petitioner and I need to check 1.a. ?
My father is the second sponsor. What does he need to check in Part 1?

Thank you
VR

[newacct]

You put "I am the petitioner" on your I-864, and your father puts "I am the only joint sponsor" on his separate I-864.