Warning! Don't use these (except for fun) unless you have a bottle of aspirin handy. I was trying to get a number of exercises into the workbooks such that teachers at different grade levels can pick and choose what they want to use. The Chevy Nova episode always catches my attention, so when I found these, I immediately thought -- use them! So I put them in and then started to analyze them. You will find many complications in these exercises. I have provided several alternate explanations, but they can get complex. (There are probably also things that I have missed.)
For students who are comfortable with clauses, perhaps the most important function of these exercises is that they demonstrate the tentativeness of grammatical explanations. Among other things, I have in mind the nature of the verb "mean." In a sentence such as
Since I try to keep the exercises to a printed page in length, I have spread these across three exercises.