①Don't try to get off the bus ----it has stopped

①Don't try to get off the bus ____it has stoppedA,while B,as C,since D,before②We'll go and see the patient ___we are busyA,even if B.for C.if D.while③---you understang this rule,you will have no further difficultyA,once B,at once C,Only D,only then