It’s easy to _________ this camera , while putting the pieces together is quite difficult, so you must keep the directions well.

A． take over

B． take apart

C． take down

D． take up

(5分) ①将黑色粉末A和无色液体B混合，生成一种无色无味的气体C；②无色气体C能使带火星的木条复燃；③加热暗紫色固体D，可同时得到A、C和E。

试推断A、B、C、D、E 各是什么物质？

A是                  B是              C是           

D是                  E是            。