Kevin,
You're absolutely right about answers to #18. They're A and D.
And I have to repeat that though this doesn't make any sense, but correct answers to #13 are A and D as well. This question is a complete mess in terms how it's formed, or better to say, in terms of how irrelevnat answers are. I figured correct answers while experimenting with different combinations of answers, when I already had 43 correct out of 44. So it turned out to be A and D.
Good luck,
Svetlana.