她学了一整夜，所以早上看起来非常疲惫。
She had been studying all night, which is why she looked so tired in the morning.
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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 表示从昨夜开始持续到早上的学习过程，结果是她早上看起来很疲惫。
She had been studying all night, which is why she looked so tired in the morning.
过去完成进行时 had been studying 表示从昨夜开始持续到早上的学习过程，结果是她早上看起来很疲惫。