用所给单词的适当形式填空
【小题1】On the _________（twenty-one）of September, we have a soccer game and a volleyball game.
【小题2】Can you _________（help）me with my math?
【小题3】All the students are busy _________（do）their homework.
【小题4】Today is my brother’s _________（thirty）birthday.
【小题5】When is our _________（sport）Day?