中国银行

单选题 The newly installed alarm system, which is directly connected to the police, will go off if the correct security code is not entered__________ 60 seconds of touching the keypad. 

A.only 
B.under 
C.within 
D.directly 

参考答案:C进入在线模考
【答案】C。解析:备选答案为副词和介词。首先应分析句子结构,判断横线处应填入介词还是副词。乍一看应填入副词修饰被动结构“is not entered”,实际上if从句是被动语态,“________60 seconds of touching the keypad”应作状语。因此横线处应填入介词,从而构成介宾短语作状语。