puzzle

a book of puns, riddles, and puzzles一本关于双关语、谜语和智力测验的书

The restaurant is trying to attract more customers, and the new menu is an important piece of the puzzle. [=an important part of what is being done]饭馆正试图招徕更多的顾客，而新菜单是关键。

Researchers are close to finding a solution, but they haven't found the final pieces of the puzzle.研究者马上就要找到解决方案了，但还有最后一道难关。

The cause of the explosion was a puzzle. [=no one knew what caused the explosion]爆炸的原因是个谜。

His strange behavior is a puzzle to his friends. [=his friends don't understand the reason for his strange behavior]他的怪异行为让朋友们大惑不解。

The question puzzled me. [=I did not know the answer to the question]这个问题令我困惑。

The cause of the accident has puzzled investigators.调查者对事故发生的原因感到不解。

I was puzzled by his behavior. [=I did not understand the reason for his behavior]他的行为让我难以理解。