【正确答案】 D

【答案解析】[解析]
Narrator
Listen again to part of the lecture. Then answer the question.
Professor
I mean, you wouldn't call it a tropical paradise or anything—ah, or maybe you would if you think about how today in some parts of the Sahara it only rains about once a century.
Narrator
Why does the professor say this:
Professor
Or maybe you would if you think about how today in some parts of the Sahara it only rains about once a century.