The unexpected question caught him off guard.

这个意外的问题让他措手不及。

同一单元的其他句子

• Life is full of the unexpected, so be prepared for anything.生活充满意外，所以要为任何事情做好准备。
• Have you ever experienced an unexpected event in your life?你曾经在生活中经历过意外事件吗？
• The unexpected rain ruined our picnic plans.突如其来的雨破坏了我们的野餐计划。
• Don't be afraid of the unexpected; it makes life interesting.不要害怕意外，它让生活有趣。
• She was surprised by the unexpected gift from her friend.她对她朋友的意外礼物感到惊讶。