Ex. And perhaps I'd better tell you,sir,once and for all,that I don't propose to allow rudeness from an impertinent young puppy. -If he had kept his temper,the negotiation would probably have been a success. -Opportunity knocks but once.Ex. –And perhaps I’d better tell you, sir, once and for all, that I don’t propose to allow rudeness from an impertinent young puppy. –If he had kept his temper, the negotiation would probably have been a success. –Opportunity knocks but once