溃疡病急性穿孔多位于
A．胃小弯十二指肠后壁B．胃大弯C．胃窦D．幽门附近、胃和十二指肠前壁
参考答案：D
Some people will never learn that you can't get something for ______. [ ]
A. something
B. anything
C. everything
D. nothing
若使用恺撒密码加密，则破译者最多尝试( ) 次即可破译密钥。
A．26
B．25
C．51
D．261
