Sometimes, it is kind of heavy to discriminate the prepositional sentence in a statement. So, to be successful finding the real main point or subject in a sentence, first, we need cross out each prepositional phrase first.
For example:
The woman on the corner is my wife.
As you can see, on the corner is the prepositional phrase being on the preposition and the corner the noun that goes along with the preposition.
If you apply this when discriminating the main subject in a sentence, you will never have a problem finding it.
Best wishes,
