—Do you know why the teacher asks for me?—He wants you to _____ your absence last night.
Apples are usually sold by ________ weight and eggs are sometimes sold by ________ dozen.
—What about ____ book? —It’s too difficult ____ book for beginners.
Whenever you are in trouble ,don’t hesitate _____us for help.
It was the longest film we have ever seen ; it ____ three hours..
___ was invented by Grain Bell..