Gratias vobis promptis pro responsis!
I suppose I can leave it as it is then. It is a bit mean of old man Wheelock to throw that in when that gerundive construction has not really been mentioned, but I have to admit that I enjoyed figuring out what I was confused about more than what I understood while going through it. Nonetheless, it could be confusing to independent learners, so I must say that he was rather mean to put that there!
flebile nescio quid queritur lyra, flebile lingua murmurat exanimis, respondent flebile ripae