口对口人工呼吸法即使操作正确，吸入氧浓度也常低于（）
A.21%
B.18%
C.15%
D.12%
E.10%
参考答案：B
设集合U={1，2，3，4}，M={x|x2-5x+p=0}，若CUM={2，3}，则实数P的值为[ ]
A. -6
B. -4
C. 4
D. 6
（）can be considered as part of risk mitigation.
A.Risk identification
B.Purchasing insurance
C.Assessment of outcomes
D.Assessment of probabilities
