屋面工程应根据建筑物的性质、重要程度、使用功能要求以及防水层合理使用年限,按不同等级进行设防,屋面防水等级共分()个等级。
A.二
B.三
C.四
D.五
参考答案:A
The police were seeking more information to find out ________ the rich merchant.
A.who was it that killed
B.who it was that killed
C.it was who killed
D.who was it killed
若对于任意x∈R,都有(m-2)x2-2(m-2)x-4<0恒成立,则实数m的取值范围是______.