—Look! A book is on the floor. Whose is it?—It ______be Rick's. It has his name on it.
My father is _______. And we just had a party for his _______ birthday last weekend.
一Excuse me, where can I exchange _______? 一There is a bank on the second floor.
Basketball is so popular a game in the world that ______ people play it for fun and exercise.
Don't be afraid of asking for help ______it is needed.
I want to know______do to improve my English.