' I can understand the SENTENCE STRUCTURE. Consider this simpler and more concrete example. Tom's car won't start.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
CliveWhat do the words 'not necessarily' refer to?Can "is" be modified? I wonder if it's the whole sentence that is modified?
I see the words 'not necessarily' as an adverbial phrase' modifying 'is'.