can't add host due to permission error

can't add host due to permission error

I have tow windows domain controller servers,due to company security policy,I don't want to give administrators group permision to monitor team,when I assign backup operators group permission,it will show access is denied error.but follow the errorr log, I  can use backup opearators group to access admin$ and c$,so the path is correct.Iwhen i give them administratos group,everything is fine.  want to know what kind permission that need.

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