请回答下列各问：

（1）登山、潜水、医疗急救时都需要用氧气，是因为氧气____ ；

实验室用高锰酸钾制氧气的化学方程式　____ ．

（2）用化学方程式回答：

稀硫酸除铁锈：　____ ；

不在溶液中发生的置换反应：____ ．

（3）野炊时，人们常把柴草架空，使燃烧更旺，请说明其中的道理：____．

2015年中央经济会议提出“一带一路”是2015年区域发展的首要战略。读“一带一路示意图”回答下列问题。

选词填空。

    Do you often eat lunch at school?How do students____about school lunches?

China

    Most schools have dining rooms．They have ____for students，for example，noodles，rice，pizza， ____，and vegetables．Most students think that Chinese food is delicious but the Western food tastes ____．

Australia

    Meat pies and cookies are all traditional ____in Australian school shops．But the country ____more attention to children's health．At school，students don't often see them．What they see is much ____food．Students can see cookies，chocolate and soft drinks only ____a week．What they often eat is healthier green foods such as sushi，corn and watermelons．

South Africa

    Most South African schools do not have meals at all．Classes ____at 1：30 pm and students get their own lunches．Many students ____food from home,usually sandwiches．Fast food sells the best among(在……中间)students．So it causes a rise in obesity(肥胖)among children．