Could you tell me which one is right and natural among the following conversational expressions? All of them convey the same idea.<br/><br/><i>1. Are you open?</i><br/><i>2. Are you open for business?</i><br/><i>3. Are you at work?</i><br/><i>4. Is this store open at the moment?</i><br/><i>5. Is it open at the moment?</i>