单选题 Listen to Track 75.

A. To compare an unfamiliar object to a familiar one
B. To reveal evidence that contradicts his point
C. To indicate uncertainty as to what deposits from glaciers look like
D. To encourage students to examine rocks in streams

【正确答案】 A

【答案解析】[解析]
Narrator
Listen again to part of the lecture. Then answer the question.
Professor
Well, uh... basically when glaciers grow and move they leave behind a distinctive deposit consisting of primarily... of, at least on the top level, of ground up little bits of rock... almost... they almost look like rocks that have been deposited by streams, if you've ever seen those.
Narrator
Why does the professor say this:
Professor
... they almost look like rocks that have been deposited by streams, if you've ever seen those.