This is the kind of mistake which the teachers haven't been able to prevent the students from making.
Which the teachers haven't been able to prevent the students from making.
S= the teachers , V= haven't been,
able is an adjective , so I think it should be a complement in the sentence.
So far, we have S V C, which is a normal grammar sentence structure.
But what about the infinitive " to prevent the students from making"
Is this another complement? But S V C C structure doesn't seem to exist.
Or is the infinitive an adverb modfiying C(able), so it remains S V C(+adverb clause)?
By the way, the PP "from making " is an adverb modifying the verb "prevent" and object of the PP is "mistake", is that correct?