以下哪一项是目前对手术器械、物品、敷料消毒灭菌中最常用的方法：（） A.高压蒸汽法

菱形、矩形、方形都具有的性质是[ ]

A. 对角线相等且互相平分    

B. 对角线相等且互相垂直平分

C. 对角线互相平分        

D. 四条边相等. 四个角相等

The number of people invited to the party ____ fifty, but a number of them ____ absent for different reasons.

A．were; was

B．was; was

C．was; were

D．were; were

I study hard ________ I may not fail in the examinations.[ ]

A．so as to  

B．in order to

C．in order  

D．so that

《切韵》是隋代（）编写的，分为（）韵。在《切韵》的基础上，北宋（）编成《广韵》。

桩身缺陷