装配式预应力混凝土构筑物壁板吊装时，其混凝土强度不能低于设计强度的（）％。
A.50
B.70
C.100
参考答案：B
句型转换。
1. Is it in the backpack?(作否定回答)
________,it ________.
2. Tom's maths book is on the floor.(对画线部分提问)
________ ________ Tom's maths book?
3. His baseball is under the table.(改为一般疑问句)
________ ________ baseball under the table?
4. His dresser is next to his bed.(改为否定句)
His dresser ________ ________ next to his bed.
5.My keys are on the sofa.(对面线部分提问)
________ ________ my keys?
在下面的IP地址中，（）属于C类地址。
A． 141.0.0.100
B．197.234.111.100
C．5.5.5.100
D． 23.46.92.100
