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

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参考答案

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。乍一看应填人副词修饰被动结构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。

1 The airline requested a__________call to ensure a seat on my flight back home.

A．confirm

B．confirmed

C．confirming

D．confirmation

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2 If the task is too complicated to figure out on__________ own, please don't hesitate to ask one of our representatives, who are here to help.

A．you

B．your

C．yours

D．yourself

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3 The hard work put in during his younger years made him become __________sound in his later years.

A．finance

B．finances

C．financial

D．financially

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