什么是血传病例？
参考答案：
通过输血或注射等方式而感染的病例
世界上人口稠密地区主要位于中低纬度近海平原，原因是 [ ]
A．这里气候温和，降水较多，地形平坦，土壤肥沃，农业发达
B．地处河流下游，水能资源丰富
C．地处沿河平原，便于欣赏海上风光
D．中低纬度地区，热量充足，降水稀少
At a college football game,
of the seats in the lower deck of the stadium were sold. If
of all the seating in the stadium is located in the lower deck, and if
of all the seats in the stadium were sold, what fraction of the unsold seats in the stadium were in the lower deck
of the seats in the lower deck of the stadium were sold. If 
of all the seating in the stadium is located in the lower deck, and if 
of all the seats in the stadium were sold, what fraction of the unsold seats in the stadium were in the lower deck