化学与环境保护、社会可持续发展密切相关，下列说法或做法合理的是（　　）

①将地沟油回收加工为生物柴油，提高资源的利用率

②进口国外电子垃圾，回收其中的贵重金属

③燃煤进行脱硫脱硝处理，减少硫的氧化物和氮的氧化物的排放

④洗衣粉中添加三聚磷酸钠（Na₃P₅O₁₀），增强去污效果

⑤易降解的生物农药更适合于在未来有害生物综合治理中的应用．

当前，发展两岸关系，实现和平统一的基础是（   ） 

Miss Fang: Hello, children. This is Mr. Xu. He's a fireman. Let's welcome Mr. Xu.

Mr. Xu: Thanks. Let's talk about ____safety today. Fire can burn down trees. It can ____people, too. We must be ____with fire. What mustn't we do in the forest or at home, children?

Peter: We mustn't ____in the forest.

Kitty: We mustn't play near fires or play with ____at home.

Mr. Xu: Very good. Safety first.