第6题: [单项选择]人工半解剖式牙的牙尖斜度为 A. 0°~3° B. 10°~13° C. 20°~23° D. 30°~33° E. 40°~43° 参考答案:C
第7题: [单项选择]Crops grew smaller in production in South Carolina mainly because ______. A. demand for cotton had decreased B. crops became varied C. planters grew richer D. soil was less productive 参考答案:D 答案解析:[解析] 事实细节题。本题是问南卡罗莱纳州农作物产量下降的原因是什么。根据文章第一段最后一句说Because the soil was beginning to wear out,crops were