#7 and #8 are the key questions. It bothered me to have more than one correct answer to #7, yet choose only one of them based on #2 (6 and 7 were the only two left that could possibly be identical). I would have liked #8 to be A or C instead of E. Yet it didn't bother me to pick an answer to #19 based entirely on other questions.
But, once I got to the point of counting how many times I chose each letter, it became pretty clear that #8 had to be E. In fact, I had to change my answer from C to E when C became impossible and got lucky that #7 was correct (and #2 and #6 and #17) regardless of which way I went. But, even not being sure of the answer to #8, the answer had to be an even number, which helped answer other questions.