The following four sentences present four different usages of the word不过. Please discuss the distinctions and connections among the four usages, illustrating your points with your own examples where necessary.1)不过二年,君必无患。2)他十七岁就结婚,一年后当了爸爸不过十八岁。3)这是个乖巧不过的孩子。4)我也没有长策,不过这种事情,其事已迫,不能计出万全的。