This note is a bit late in coming, but in case people are still working on the homework:

Part 6 asks you to work with the sentence One morning I shot an elephant in my pajamas, using a couple of our constituency tests. The thing is, with one morning in there, this results in some kind of awkward-sounding sentences, but they are awkward in a way that isn’t really important. One morning is a kind of adverbial phrase that you could just as easily leave out. I’d suggest actually just dropping that from the sentence altogether and analyzing it as if it were just I shot an elephant in my pajamas. Alternatively, it’s ok if you want to put one morning at the end of the test sentences (rather than at the beginning).

At least to me, even unchanged, the test sentences don’t sound terrible, it just winds up sounding more like poetry or something, not terribly natural but still clearly English.