A、City tiles. B、Slate or stone. C、Wooden shingles. D、Reeds or straw. D这是一道细节题。文章提到“17世纪的殖民主义者用芦苇或麦秆来盖屋顶”，因此 正确答案是D。

Listen as a guide describes the ancient art of thatching a roof.
    Welcome to the Four Winds Historical Farm, where traditions of the past are preserved for visitors like you. Today, our master thatchers will begin giving this barn behind me a sturdy thatched roof able to withstand heavy winds and last up to a hundred years. How do they do it? Well, in a nutshell, thatching involves covering the beams or rafters--the wooden skeleton of a roof--with reeds or straw. Our thatchers here have harvested their own natural materials for the job--the bundles of water reeds you see lying over there beside the barn.
    Thatching is certainly uncommon in the United States today. I guess that’s why so many of you have come to see this demonstration. But it wasn’t always that way. In the seventeenth century, the colonists here thatched their roofs with reeds and straw, just as they had done in England. After a while, though, they began to replace the thatch with wooden shingles because wood was so plentiful. And eventually, other roofing materials like stone, slate, and clay tiles came into use.
    It’s a real shame that most people today don’t realize how strong and long-lasting a thatched roof is. In Ireland, where thatching is still practiced, the roofs can survive winds of up to one hundred ten miles per hour. That’s because straw and reeds are so flexible. They bend but don’t break in the wind like other materials can. Another advantage is that the roofs keep the house cool in the summer and warm in the winter. And then, of course, there’s the roofs’ longevity—the average is sixty years, but they can last up to a hundred. With all these reasons to start thatching roofs again, wouldn’t it be wonderful to see this disappearing craft return to popularity?
26. What is about to be demonstrated?
27.What are thatched roofs made of?
28.According to the speaker, why did thatching die out in the United States?
29.According to the speaker, why does thatch survive strong winds?
30.According to the speaker, how might thatching become popular again?