我们非常努力地想发动那辆旧车，但所有的努力都失败了。
We tried very hard to start the old car, but all our efforts were unsuccessful.
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unsuccessful英 /ˌʌnsəkˈsesfʊl/|美 /ˌʌnsəkˈsɛsfʊl/
解释
unsuccessful 是由前缀 un-（表示“不、非”）和形容词 successful（成功的）组成的形容词，意思是“不成功的、失败的”。
We tried very hard to start the old car, but all our efforts were unsuccessful.
unsuccessful 是由前缀 un-（表示“不、非”）和形容词 successful（成功的）组成的形容词，意思是“不成功的、失败的”。