What does “If you only have as much sense in your head as you have hairs in your beard” on the last paragraph mean…

A
Get organized and do things effectively.

B
 To stop thinking or behaving foolishly.

C
Stuck in a difficult circumstance with no escape.

D
Putting efforts into something that is not worthwhile result.

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What does “If you only have as much sense in your head as you have hairs in your beard” on the last paragraph mean…