以土地所有权为抵押物设立的抵押，其抵押合同( )
A．自合同订立时生效
B．自办理抵押登记时生效
C．自土地管理部门批准后生效
D．无效
参考答案：D
Jack tried to play a trick ____ his sister but she was not taken____. [ ]
A. in; in
B. by; on
C. on; on
D. on; in
金属材料承受三向压应力的压力加工方法是（）
A.轧制
B.挤压
C.冲压
D.拉拔
