But which one was right?
They were all right! All three patterns made sense, and helped you produce meaningful variations.
If you really wanted to know whether main noun + prepositional phrase or focus + main noun is the right way to look at the snippet, the best way is to read the snippet aloud and listen to where the emphasis lands for you, because that will tell you what you consider to be the main noun:
- The greatest of these was fear.
- The greatest of these was fear.
Both readings make sense, they just have different emphases, and that is enough to subtly change our grammatical analysis.
But again, the lesson you want to take from this is that even simple sentences can have hidden depths, and you can explore these by being logical, systematic, and experimentally-minded, and by trying the different language tools you’ve learned in these lessons.