下列说法正确的是

下图是产生和收集气体的实验装置示意图，该装置适合于(　　)

已知函数f（x）=lg（3+x）﹣lg（3﹣x）

先通读下面的短文，掌握其大意，然后从A、B、C、D四个选项中选择可以填入空白处的最佳答案。    Do you have a good friend? I have one. She's English and1name is Kate.We are in the same (相同的)2and my desk is next to hers.She is nice and I3her well.She always4me with my English and I always tell her how to say "quilt", "grandma", "radio" …in Chinese.She likes reading and she has so many5in her room.They are everywhere — on her bed, on the sofa and on her desk ...Some of them are6the computer.She7it's very important(重要的).Look! This is a8of Kate's family.9people(人)are in it：her parents.her sister, her brother and herself(她自己).Kate's mother Helen is our English10.She teaches well and she's good to us.We like her very much.

一小时前我们分组讨论了此事。

An hour ago we____ ____ ____ ____it in groups.