已知正实数数列$\left\{a_n\right\}$中，$a_1=1,a_2=2,2{a_n}^2={a_{n+1}}^2+{a_{n-1}}^2\left(n\ge 2\right)$，则$a_6$等于（   ）

计算出下列圆柱的侧面积．

侧面积是____  $d{m}^2$  

5吨煤烧了 $\frac{1}{5}$ 后，还剩4吨．（判断对错）

肺泡数量很多，外面包绕着____；肺泡壁和毛细血管壁都很薄，都是由____层上皮细胞构成的，这些特点有利于____和____之间进行气体交换．

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.