我当时年轻得多，而且非常天真。

I was much younger then, and very ___naive.

这可能听起来有点理想主义和天真，但我认为这种沟通概念会让世界变得更美好。

It might sound a bit idealistic and ___naive, but I think this concept of communication will make the world a better place.

他对投资的天真方法导致了重大损失。

His ___naive approach to investing led to significant losses.