茫然不知所措

dāng lǎo shī wèn wǒ wèn tí de shí hou wǒ máng rán bù zhī suǒ cuò

当老师问我问题的时候我茫然不知所措。

I was all at sea when the teacher asked me the question.

tā máng rán bù zhī suǒ cuò

他茫然不知所措。

He is at a loss about what to do.