找到这个问题的解决方案仍然难以捉摸。

Finding a solution to this problem remains ___elusive.

实现世界和平是一个难以企及的梦想。

Achieving world peace is an ___elusive dream.

幸福的概念常常难以捉摸，难以定义。

The concept of happiness is often ___elusive and hard to define.