他们进行了数次不成功的尝试，以营救被困的徒步旅行者。

They made several ___unsuccessful attempts to rescue the stranded hikers.

她的工作申请没有成功，所以她继续寻找。

Her job application was ___unsuccessful, so she kept looking.

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.