The question caught her completely off-guard and she did not know how to reply.
这个问题令她猝不及防，不知道怎么回答。
Her betrayal took me completely off guard.
她的背叛让我完全措手不及。
A border guard grumbles that the only tourist in weeks has set off her tripwire.
一个边防人员抱怨说，几个星期只来了这么一位游客，还就触发了她负责的虚拟警戒线。
The teen says the outpouring of support caught her off guard.
But the digital age can still catch her off guard.
He was caught off guard, and tried to explain, then comfort her.