—More and more foreigners are becoming interested in Beijing Opera.—That's true. It's an important p

题干

—More and more foreigners are becoming interested in Beijing Opera.

—That's true. It's an important part of Chinese .

A：culture

B：invention

C：custom

D：influence

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A

（Ⅰ）当m=6，n=100时，

（ⅰ）若数列A₆：11，78，x，y，97，90是一个“好数列”，试写出x，y的值，并判断数列：11，78，90，x，97，y是否是一个“好数列”？

（ⅱ）若数列A₆：11，78，a，b，c，d是“好数列”，且a＜b＜c＜d，求a，b，c，d共有多少种不同的取值？

（Ⅱ）若数列A_m是“好数列”，且m是偶数，证明： $\frac{a_{1} + a_{2} + \dots + a_{m}}{m} \geq \frac{n + 1}{2}$ ．