他整晚都在学习，所以考试开始时已经筋疲力尽了。
He had been studying all night, so he was exhausted by the time the exam started.
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had英 /hæd/|美 /hæd/
been英 /biːn/|美 /bɪn/
studying英 /ˈstʌdiɪŋ/|美 /ˈstʌdiɪŋ/
解释
过去完成进行时 "had been studying" 说明学习从过去某时开始一直持续到考试开始时，动作的延续导致其后状态。
He had been studying all night, so he was exhausted by the time the exam started.
过去完成进行时 "had been studying" 说明学习从过去某时开始一直持续到考试开始时，动作的延续导致其后状态。