Which of the following contributes to the theme?
A.
The real tree is more detailed and smells fresher than the plastic trees that line the streets.
B.
The inside tour of the O'Brien home is not as impressive as the narrator had hoped.
C.
Old structures and trees were destroyed during the Boston urban-renewal campaign.
D.
The narrator collects and pockets an acorn from the grass by the tree before he leaves.

I saw my first tree today. Oh, I've seen the plastic trees; practically every street has a few of them.
The O'Brien home was one of the few examples of old-style wooden structures that hadn't been demolished in Boston's urban-renewal campaign at the turn of the century.
The home itself was unimpressive. It had none of the marble gloss or steely sheen of modern buildings but was rather a dull white color, with the paint peeling in places.
My mind was on the tree, and I thought the inside tour would never end, but soon we were walking through a doorway hidden in one of the bookshelves and into the back yard. The yard was big — at least 10 by 20 feet — and I was surprised to find real grass growing on the sides of the concrete walkway built for tourists. The grass didn't distract me for long, however, because I just couldn't help noticing the tree!
It was located at one end of the yard, and there was a mesh fence around it for protection. It was similar in form to the plastic trees I'd seen, but there was much more to it than that. You could see details more intricate than in any artificial plant. And it was alive. But best of all was the smell. It was a fresh, living odor, alien to the antiseptic1 world outside with all its metal, plastic, and glass. I wanted to touch the bark, but the fence prevented me from doing so. The three of us stood there for a moment, and then the tour guide told us to make room for the next group. I didn't want to go — in fact, I felt almost like crying.
On the way back home, Mom and Dad were silent, and I read through one of the brochures the guide had passed out. When I came to the part that said the O'Brien home would be open only for the rest of this year, I was sad. They intend to tear down the place to make room for some kind of insurance building, and the tree will have to go, too.
For the rest of the trip, I just sat still, fingering the object in my pocket which I had picked off the grass in the O'Brien's back yard. I think it's called an acorn.
1. very clean, especially as to be bland