I suspect the one I missed had to do with confirmation. In any case, considering I've never read the Baltimore Catechism, I did pretty well. Of course, that's not saying I agree with all the answers I gave; I was answering from my understanding of what the RCC's official positions were.
If I were constructing the test to be statistically valid, however -- if I were using it to actually grade somebody or as a research tool -- I would be more careful in constructing the answers. Too many right answers stood out in form or tone from the blinds: a test-smart taker would probably score pretty high, without much specific knowledge of RC teaching.