[Part 11] Raymond Smullyan's Certified Knights and Knaves puzzles A new puzzle

Here is a completely new puzzle that (as far as I know) isn't in any of Smullyan's or anybody else's books:

Every day on the island, I kept meeting natives and over time started to invent my own labels for them. For example, when two natives had a different type, i.e., knight versus knave, and a different certification status, i.e., certified versus uncertified (in any order), I thought of them as "full opposites".

One day, I met three natives A, B, and C. I knew nothing about A and B, and all I already knew about C (based on an earlier encounter) was that she was uncertified. During our brief encounter, A and B each made one statement that allowed me to infer that they were complete opposite of each other, but that neither one of them was a complete opposite of C. I was also able to infer that exactly one of my three interlocutors was a knave.

Which two statements would work? 

Can you solve this puzzle?

If so, can you find a "better" solution than mine?

How do you rank solutions anyway?

I can't wait to read your comments!

SPOILER: My answer appears below.

Here is my solution:

A: "I am certified, C is a knight, but B and I are not both knights."
B: "Either A and I are knaves or else I am certified and C is a knight."

that I obtained by translating the following two formulas:

A <-> ((-A | -B) & (Ac & C))

B <-> ((-A & -B) | (Bc & C))