Correct

一问三不知

/ yī wèn sānbùzhī /
Strokes

Definition

lit. to reply "don't know" whatever the question (idiom)/fig. absolutely no idea of what's going on/complete ignorance

Example

Definition

say ‘I don't know' to every question—not know a thing; be entirely ignorant

1
Biè
wèn
le
  
,
zǒngshì
总是
wènsānzhī
一问三不知
  

Don't ask him any questions—he never knows the time of day.