I don’t know the origin of this custom.

People still don’t know how languages get originated.（)

I was out of town at the time, so I don’t know exactly how it _______.A. was happening

I don’t know the origin of this custom.

I don’t know if the pain.ting is authentic

I don’t know if the pain.ting is authentic

I don’t know the 【origin】 of this custom.A.nature