---Cliff, I lost your ball at school. I suppose I should pay for it. ---Oh.____. It was just an old ball anyway.
Teaching is a difficult job ______ requires great skill and patience.
Drivers must stop when the traffic lights _____ red.
There was an excited expression ______ his face when he heard the good news.
Milk will turn sour soon on hot days ______ it is stored in the refrigerator.
You'd better not ride the bicycle on snowy days; you ______ fall.