已知向量$\overrightarrow{m}=(\lambda +1,1),\overrightarrow{n}=(\lambda +2,2),$若$(\overrightarrow{m}+\overrightarrow{n})\perp (\overrightarrow{m}-\overrightarrow{n})$，则$\lambda =$   （    ）

如图为元素周期表中钠元素的相关信息，下列说法正确的是（ ）

用括号内所给单词的适当形式填空,必要时可加助动词或情态动词。
Waste can be seen everywhere in our school. Some students ask for more food than they can eat and others often forget____ (turn)off the lights when they leave the classroom. They say they can afford these things. But I____ (not agree)with them.Waste can bring a lot of problems. Although China is rich in some resources (资源), we're short of others, for example, fresh water(淡水). It____ (report) that we will have no coal(煤) or oil to use in 100 years. So if we go on____ (waste) our resources,what can we use in the future? Think about it. I think we should
say to the students who waste things every day. Everybody____ (stop) wasting as soon as possible.
In our everyday life, we can do many things____ (prevent) waste from happening, turn off the water taps(龙头) when we____ (finish) washing, turn off the lights when we leave the classroom, try not to order more food than we need, and so on. Little by little, everything will be changed. Waste can be stopped one day if we do our best.