Question on form I-485 ,Application Type : Part 2

[US2016]

I am in the US on temporary work visa (H1B) valid until mid 2018. I am married to a US citizen 6 months ago and I am applying for family based Green card by filling I-130 and I-485 together. I have a question about I-485 Part2 'Application Type'. I checked 'a' box on part2 as the other options doesn't apply to me. Is this correct? Thanks in advance.