Correct

挠头

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Strokes

Definition

tricky/problematic/difficult/to scratch one's head (in puzzlement)

Example

As a Verb

scratch one's head—hard to tackle

1
Zhè
这
shìr  
事儿
zhēn
真
ràng
让
rén
人
náotóu
挠头
  
。

This is really a knotty problem.