测定某地100名正常成年男子的血红蛋白量，要估计该地正常男子血红蛋白均数，95%可信限范围为（）
A.A
B.B
C.C
D.D
E.E
参考答案：D
数列{an}中，S1=1，S2=2，S n+1﹣3Sn+2S n﹣1=0（n≥2），求数列的通项an以及数列前n项和Sn．
The nurse is preparing to begin one-person cardiopulmonary resuscitation. The nurse should first
A．establish unresponsiveness.
B．call for help.
C．open the airway.
D．assess the client for a carotid pulse.
