TOEFL Reading: ETS-TOEFL阅读机经 - L400NAVH4_7N78Z_L$

Which of the following is mentioned in paragraph 3 as an effect of Sumerian trade? A. The spread of Sumerian civilization to people outside Sumer B. The discovery of copper C. A rise in the price of textiles, pottery, and other goods sold within Sumer D. An increase in the scarcity of stone within Sumer