某人研究了吸烟与肺癌的关系,结果90个病例中60人有吸烟史;90个对照中40人吸烟。据此计算OR为()
A.1.5
B.2.5
C.3.0
D.2.0
参考答案:B
汽包水位报警高/低二值是()
There are _____ books in the school library. [ ]
A. lots of
B. much
C. a little
D. a lot