已知函数$f\left(x\right)=\frac{1}{3}{x}^3+x^2+ax+1$，若函数f（x）在区间﹣2，a上单调递增，则实数a的取值范围是____ 

给下面的句子选择合适的答语。

①Happy birthday! ____   A. Two books.

②How old are you? ____   B. Thank you.

③How many books? ____   C. You're welcome.

④Let's eat the cake. ____   D. I'm 10.

⑤Thank you. ____   E. Great.

据材料一，分析玛雅人的哪些方面可以成为研究其社会生活的着手点？并结合所学知识，分析这些方面在玛雅文明中产生了哪些影响？