He stretched up his arms in a vain effort to reach the top of the embankment.他伸直了双臂徒劳地想要抓到堤岸的顶部。A vain effort to quell the public's fears only made matters worse.旨在消除公众恐惧的努力毫无结果，反而把事情变得更糟了。I was singing in a vain effort to cheer him up.我唱歌试图让他高兴起来，结果是白费力气。