(1)连接词：if, once, as long as, on condition that
eg：If winter comes can spring be far behind.
As long as it doesn't rain, we can play.
You can go out on condition that you wear an overcoat.
Modern cars are far tougher to steal, as their engine management computer won't allow them to start unless they receive a unique ID code beamed out by the ignition (点火) key.