Waste paper, waste glass, and waste iron can all be _____.
---Jack can't concentrate on his study recently. --- Yes, that might ____ why he did so badly in the last test.
I can hardly remember any occasions ____ I get caught in a traffic jam in our town.
Holiday shopping ___be a tiring experience.There are so many places to visit and choices to make.
If a book is in French, ____ will be a challenge for me.
Mrs Green was so pleased ____ her daughter won the first place in the singing competition.