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If you ask someone working at a store 'Where's milk?' would that be right grammatically or does it have to be 'Where's the milk?' I know in the kitchen you would say 'Where's the milk?' or 'Where's the salt?' but i'm not sure if it would be the same case here perhaps because in the store you would be talking about milk in general. Even if 'Where's milk?' is wrong, then why does 'Where's milk in this store' sound right?