题目

     Imagine you are an astronaut, you find a new planet that looks like the earth, and when you want to put the flag on it, you find out that this planet has already got population. What would you do?      The US astronaut, Charles “Chuck” Backer, in the new cartoon film Planet 51 just comes across this thing.      Planet 51 is a place where there is no human being. So Chuck arrives in the planet and wants to name it “the US”. But he suddenly finds himself surrounded by lots of little green aliens.      These aliens live in fear that they may be invaded by str工业上用铝土矿(主要成分为Al2O3·xH2O，Fe2O3、SiO2等)提取纯Al2O3做冶炼铝的原料，提取时操作过程如下图，指出图中操作错误的是A.④⑤B.③④C.②⑤D.①②