用after、 before 、if 、when、 while 、as soon as 填空 用after、 before 、if 、when、 while 、as soon as 填空 1.Never get on or off a bus ( )it is still running. 2.All thing are difficult( )they are easy. 3.I'll talk about it with you ( )we meet next week. 4.( ) I left school at the age of seventeen,I want to college.