如果你想表达困难的问题，你可以使用以下几个英语短语：

"A tough question" 意思是困难的问题。

"A challenging question" 意思是具有挑战性的问题。

"A difficult question" 意思是困难的问题。

"A perplexing question" 意思是令人困惑的问题。

"A conundrum" 意思是一个棘手的问题。

例如：

"This math problem is a tough question. I'm having a hard time figuring it out."

"This philosophy exam is full of challenging questions. I need to really think hard to come up with the right answers."