Deep understanding of context-free grammar

The room was very full and who were they all?

I was almost swept past the subway, so swiftly were the people milling around on the sidewalk.

The inner door, which led to the passage, which in turn led to the storm door, was beside the stove.

His glasses are thick, magnifying, and his eyes, puffed and swimming, seem not to miss a thing.

I was tormented by strange hallucinations.

What's mine is yours, and what's yours is mine.