unavailing
adj. 无效的；徒劳的；无益的；无用的
例句
Their efforts were unavailing.
他们的努力都付诸东流。
《牛津词典》
Efforts to reach the people proved unavailing.
接近人群的努力被证明是不成功的。
《柯林斯英汉双解大词典》
But all my efforts appeared unavailing.
但是，我的努力似乎是白费劲。
