I was just writing this out! I believe practice in unit testing is what let me get this question right. I almost submitted n^1, n^2, n^3 before I realized I didn't get any wrong answers and something didn't feel right. I credit this 'instinct' to having written thousands of tests, and trying to make them fail to make sure my tests weren't lying to me.
It's funny. Even though I got the right answer, looking back, I still see many holes in my tests. I only tested positive and negative integers. I didn't even think to try fractions, decimals, hex values, text, etc. and I was already expecting a confirmation bias test.