题目

Welcome to the Amazing kids Website! Here you can read about clever children all over the world. Gina, who is thirteen years old, got first prize in the “Young Look of the Year” competition and is now writing her own recipe (烹饪) book for kids. I want it to be fun to read and easy enough for children to use, she says. Gina learned by observing （观察）her father, who's also good at cooking, in the kitchen. She wants to encourage other children to cook because everyone needs to eat, so it's a skill that will always be useful!Fourteen-year-old Bren used to love running until he had a 根据“绿色化学”的思想，某化学家设计了下列化学反应步骤: ①CaBr2+H2OCaO+2HBr  ②2HBr+HgHgBr2+H2③HgBr2+CaOHgO+CaBr2  ④2HgO2Hg+O2↑该方案的目的是为了制备A.HBr                   B.CaO                   C.H2                   D.Hg