已知函数$f\left(x\right)=a·2^{\left|x\right|}+1\left(a\ne 0\right)$,定义函数$F\left(x\right)=\left\{\begin{array}{c}f\left(x\right),x>0\\ -f\left(x\right),x<0\end{array}\right.$ 给出下列命题:
①$F\left(x\right)=\left|f\left(x\right)\right|$; ②函数$F\left(x\right)$是奇函数;③当$a<0$时,若$mn<0$,$m+n>0$,总有$F\left(m\right)+F\left(n\right)<0$成立,

其中所有正确命题的序号是（　）

空气成分中体积分数最大的物质是____；地壳中含量最多的金属元素与氧元素所形成化合物的化学式为 ____.

21世纪化学的最新定义为“化学是一门创造新物质的科学”．下列有关说法不正确的是（　　）

They can't buy anything because _________ of the shops are open now

根据材料内容，选择正确答案。  

    There are 50 students in Class 8. Now they are doing a survey about how they spend their pocket money. Some spend it on books, and others spend it on visiting. What about you? Please read the form and answer the questions.