参考答案

正确答案：B
解析：Listen again to part of the lecture and then answer the following question.
"Later, at the end of the 1800s, when the railroads brought materials such as asphalt shingles, tar paper, and finished boards to the frontier, the sod house was abandoned for one-room board shanties, covered with tar paper. Whether this was an improvement is subject to debate."
Why does the professor say this:
"Whether this was an improvement is subject to debate."
To demonstrate uncertainty