题目

根据首字母提示确定需要填写的单词We usually have three meals a day, breakfast, lunch and supper. Which meal willc    us the fewest health problems if we have to miss one ? Most people would rather not have breakfast, especially teenagers. They just eat some snacks or fast food i   . What will happen if we do like this?Many scientists and doctors in the field of health consider breakfast to be the m    important meal of the day. If we eat a good breakfast, they say, we will have e    energy we need to begin our working d根据下列现象或描述，请你将空气中存在物质的序号填写在空白上，（A氧气 B二氧化碳 C水蒸气 D氮气 E稀有气体）。①小白鼠在装有空气的密闭容器中可存活一段时间，说明空气中含有__________；②可燃物能在空气中燃烧__________；③空气是制造氮肥的原料___________；④酥脆的饼干在空气中放置，过一段时间后变软__________；⑤石灰水长期露置在空气中，瓶壁和石灰水底部均会出现白色固体物质，说明空气中有__________。⑥空气中的各成分按体积分数最大的气体是__________。