用DJ6经纬仪观测水平角，要使角度平均值中误差不大于3"，应观测（）个测回。
A．2
B．4
C．6
D．8
参考答案：D
解析：
An analyst does research about defensive internal ratio and gathers the following information about a company (in millions): · Current ratio is 2.5 ·Quick ratio is 2 ·Cash ratio is 1.5 ·Average daily expenditures is $20 ·Current liabilities is $100 The company's defensive interval ratio is closest to:（）
A. 7.5
B. 10.0
C. 12.5
下面哪一个不是烫伤的急救方法？（）
A.离
B.包
C.热
D.送
