二次函数y=x2-2x+2的顶点在第( )象限.
A.一
B.二
C.三
D.四
∵y=x2-2x+2=(x-1)2+1
∴抛物线顶点坐标为(1,1),在第一象限,
故选A.
. Have you decided ______ the color of your new car?
A.on
B.for
C.with
D.at
某血站实验室用20个室间质评品测某厂家抗HIV试剂的灵敏度.特异性,结果10个已知阳性中测得8个阳性.2个阴性,10个已知阴性中测得6个阴性.4个阳性,该试剂的灵敏度.特异性分别是:()
A.80%.70%
B.90%.80%
C.70%.60%
D.80%.60%