TOEFL Listening: ETS-TOEFL听力机经 - 3VO1BI83184S9F38P$

What does the professor say were two important factors in the decline in silver mining in Park City, Utah? A. The increasing cost of extracting silver B. A decline in the price being paid for silver C. The higher wages being paid to miners in other places D. A national downturn in economic activity