①Don'ttrytogetoffthebus____ithasstopped
A,whileB,asC,sinceD,before
②We'llgoandseethepatient___wearebusy
A,evenifB.forC.ifD.while
③---youunderstangthisrule,youwillhavenofurtherdifficulty
A,onceB,atonceC,OnlyD,onlythen