put their finger on不清楚
例句:Mary has been in hospital for several days but the doctors seem unable to put their finger on that is wrong. 
      玛丽住院好几天了,可医生好像弄不清病因。 
      I can't quite put my finger on what's wrong. 
      我找不出错在什么地方。 
2.Least of all parents of those who died.
least of all最不, 尤其
例句:I like that least of all.
      我最不喜欢那个。
      Nobody need worry, you least of all.
      谁也不用担心, 尤其是你。