某钠电极，其选择性系数KNa+，H+约为30。如用此电极测定PNa等于3的钠离子溶液，并要求测定误差小于3%，则试液的PH值应大于（）。
参考答案：6
As a result of the earthquake, two-thirds of the buildings in the area _____. [ ]
A. need repairing
B. needs repairing
C. needs to be repaired
D. need to repair
一般病人术前血清白蛋白大于多少方可手术（）。
A.10g／L
B.15g／L
C.20g／L
D.25g／L
E.30g／L
