o Had we known it in time we would have prevented the accident 要是我们及时知道那件事,事故本来 是可以防止的。(虚拟语气) After watching for years he discovered important phenomena 观察了数年之后他发现了许多重要现象 (数)⚫Had we known it in time, we would have prevented the accident. 要是我们及时知道那件事， 事故本来 是可以防止的。（虚拟语气） After watching for years, he discovered important phenomena. 观察了数年之后他发现了许多重要现象。 （数）