有些射性元素要经历一系列的衰变才能稳定，关于X、Y、Z三个原子核的衰变方和如下：

X→ ${}_{82}^{206}$ Pb+8 ${}_2^4$ He+6 ${}_{-1}^0$ e    

Y→ ${}_{82}^{207}$ Pb+7 ${}_2^4$ He+4 ${}_{-1}^0$ e 

Z→ ${}_{82}^{208}$ Pb+6 ${}_2^4$ He+4 ${}_{-1}^0$ e

根据以上方程可以推断在X、Y和Z中，下列正确的是（   ）

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运用所学知识回答： 

   A lift is wonderful. It is really only a small room. Rooms usually stay in one place. Lifts travel up and down all day long.
    Sometimes a worker stands in the lift. He or she operates it up and down. In modern lifts there is no worker.  People walk in. They know which floor they want. They push a button and the lift goes to that floor. It is all very fast and easy.
   Lifts are very important to us. Why? Think about a tall building. Maybe it has twenty floors. Maybe it has fifty or more. Who can walk up all the stairs? Maybe people can climb them one time. Can someone climb thirty floors to an office every day? Can small children walk up to their room on the twenty-fourth floor? Can their mothers and fathers carry food up all those stairs? Of course not.
   We can have high buildings because we have lifts. We could not have all the beautiful tall buildings in the world without lifts. They are really wonderful.

①各取0.1mol分别充分燃烧，其中B、C、E燃烧所得的CO₂均为4.48L（标准状况），A和D燃烧所得的CO₂都是前三者的3倍；

②在适宜条件下，A、B、C都能跟氢气发生加成反应，其中A可以转化为D、B可以转化为C，C可以转化为E；

③B和C都能使溴水或酸性KmnO₄溶液褪色，而A、D、E无此性质；

④用铁屑作催化剂时，A可与溴发生取代反应．

判断A、B、C、D、E各是什么物质，写出结构简式A____B____C____D____E____．