1.different是形容词,这里要填的是它的名词形式,又因为这里是指两个单词的区别,所以在用复数.因此,要填：differences
2.thing不可以用在疑问句中,所以,这里要填anything.
anything
1) 任何事情/东西,可以用在肯定句/否定句/疑问句中.
如:You can take anything you like.Do you have anything to say?
There is not anything you like here.
2)something 的疑问/否定形式.
如：--Is there anything in the box?--No nothing.
He has not anything to do today.
3.从A句中可以判断出时态为现在时（从does看出）,所以,B句的时态要用现在进行时,又因为主语是“A group of chidren ”,为第三人称复数,那么,这里要填的是celebrate的现在进行时,即为are celebrating.