at a loss 不知所措；困惑；茫然

【例句】
These troubles came along all at the same time that I was at a loss.
这些乱子突然一起发生，使我不知所措。

However, how to work in penetrating life education has made a lot of class teachers at a loss.
可是，如何在工作中渗透生命教育却让很多班主任不知所措。