They have been in the library since_______.A:a long time agoB:it had been openC:eight o'clockD:two hours应该选哪个?为什么?

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They have been in the library since_______.A:a long time agoB:it had been openC:eight o'clockD:two hours应该选哪个?为什么?

They have been in the library since_______.A:a long time agoB:it had been openC:eight o'clockD:two hours应该选哪个?为什么?
They have been in the library since_______.
A:a long time ago
B:it had been open
C:eight o'clock
D:two hours
应该选哪个?为什么?

They have been in the library since_______.A:a long time agoB:it had been openC:eight o'clockD:two hours应该选哪个?为什么?
很高兴为您
选C
since的用法:译作“自从…以来”
(1)接时间点:如 I have stayed in that country since 1995.要求:谓v.用现在完成时,而且须是延续性动词.
(2)接一段时间 + ago:如 They have lived in that house since two years ago.要求:谓v.用现在完成时,而且须是延续性动词.
(3)接时间状语从句:如 I have loved her since I met her last time./ Lily has stayed at home since she left school.要求:主句的谓v.用现在完成时,而且须是延续性动词;从句的谓v.用一般过去时,而且须是终止性动词.
(4)用于句型“It’s / It has been + 一段时间 + since + 时间状语从句”中,译作“自从…以来,已经…(时间)了”.如 It’s / has been three months since he moved to this city.要求:主句的谓v.用一般现在时或现在完成时;从句的谓v.用一般过去时,而且须是终止性动词.
(5)用于句型“一段时间 + has passed since + 时间状语从句”中,译作“自从…以来,…
(时间)已经过去了”.如上个例句还可写成:Three months has passed since he moved to this city.要求:主句的谓v.用现在完成时,而且动词必须是has passed;从句的谓v.用一般过去时,而且须是终止性动词.
(6)注:当since用于否定句时,主句的谓v.可以是终止性动词.如 He hasn’t seen the film since last month.
(7)相关词组:“从那时起”:ever since、since then、from then on.
注:ever since作为一个词组,放句尾可单独使用.如I have given up smoking ever since.另外,还可在since后接句子.since前加ever,只是加重语气而已.如 I have given up smoking ever since I caught a bad cough.
(8) since还可引导原因状语从句,译作“由于;因为”,相当于because.如 Since he was lazy,he didn’t finish his homework.

选A,since是自从的意思。

c
排除法 A 不用加since就可以 B 时态不对 D 缺少句子成分

C