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?: Hook-Theory 3.6 ...brick wall

Context:
Thus far I’ve aced all the questions.
but this one stopped me in my tracks.

This tells me I don’t understand this concept.
I know what stable scale degrees are
(scale degrees that a sounding chord entails)
I know what unstable scale degrees are
(not that)
I know what strong and weak beats are
I know what resolution is
I aced all of the questions in all of the other sections up to this point.

I can even list out the scale degrees of each chord
(i did that on paper to try and figure out the question)
I 1, 3, 5
ii 2, 4, 6
iii 3, 5, 7
IV 4, 6, 1
V 5, 7, 2
vi 6, 1, 3
vii 7, 2, 4

But yeah…
Even when I gave-up and read the answer…

Something isn’t connecting in my head here.

Suggestions?
is there a way to drill this?
level up my understanding?
(I am sub-scribed to chord crush. is there perhaps something in there that can help me?)