新型储氢材料是开发利用氢能的重要研究方向．

已知函数$f\left(x\right)=\left|x^2-6\right|$，若$a<b<0$,且$f\left(a\right)=f\left(b\right)$，则$a^{2}b$的最小值是（  ）

根据对话内容，在空白处填入恰当的句子，使对话完整、通顺。

A：Hi, Alex．You look tired．Why?

B：Because I stayed up late last night．

A：____?

B：I had to finish my homework．I'm taking a class online these days．

A：Really!____?

B：I'm taking an art class．

A：Is it difficult to learn?

B：____．But I have to spend a lot of time doing homework．

A：____?

B：I think it's very useful．I can learn a lot about art．

A：That's great．Is the class cheap?

B：Yes，it's cheap，and also helpful． ____?

A：Great．I'd love to．

近年来，某市建设了多座“漂流书亭”，投放几万册图书，用“带一本书来，换一本书走”的方式，让该市“满城书香”。这一举措旨在（    ）