用所给词的适当形式填空
____ Why all the _________ (smile) faces? .
____ We will take __________(turn) to clean our classroom.
____ These stories end with ___________(happy)and laughter .
____ ________ (wear) different colors of clothes can affect our feelings.
____ I ______________(not,pass) the English exam,so I was so sad.

如图所示，超声波加湿器是利用超声波振动时具有____，将水滴击打成为非常小的雾滴，喷洒到空气中增加“湿度”的；医院里用____ 线杀死微生物，达到灭菌的目的。

多音字组词

朝zhāo____     cháo____   奔bēn____      bèn____

方程２ｘ－３ｙ＝５，ｘｙ＝3，x+$\frac{3}{y}$=3，３ｘ－ｙ+２ｚ＝０，x²+y=6中是二元一次方程的有（    ）个。