If sheila wants to decrease her dog barking at the cat next door, she should most likely use

If sheila wants to decrease her dog barking at the cat next door, she should most likely use punishment.

She can not give her dog a treat, which the dog will understand as a tragic punishment because it is a known fact that dogs love their treats. So each time it barks at the cat, it won't get a treat. Once it realizes that, it will stop barking because it will want its treat back.