先阅读下列材料，然后解答问题：
材料1　从3张不同的卡片中选取2张排成一列，有6种不同的排法，抽象成数学问题就是从3个不同元素中选取2个元素的排列，排列数记为A₃²＝3×2＝6.
一般地，从n个不同元素中选取m个元素的排列数记作A_n^m，
A_n^m＝n(n－1)(n－2)…(n－m＋1)(m≤n)．
例：从5个不同元素中选3个元素排成一列的排列数为：A₅³＝5×4×3＝60.
材料2　从3张不同的卡片中选取2张，有3种不同的选法，抽象成数学问题就是从3个元素中选取2个元素的组合，组合数记为C₃²＝$\frac{3\times 2}{2\times 1}$＝3.
一般地，从n个不同元素中选取m个元素的组合数记作C_n^m，
C_n^m＝ $\frac{n\left(n-1\right)\cdots n-m+1}{m\left(m-1\right)\cdots 2\times 1}$(m≤n)．
例：从6个不同元素中选3个元素的组合数为：
C₆³＝$\frac{6\times 5\times 4}{3\times 2\times 1}$＝20.
问：(1)从7个人中选取4人排成一排，有多少种不同的排法？
(2)从某个学习小组8人中选取3人参加活动，有多少种不同的选法？

读“海洋酸化示意图”(ΔpH代表pH值的变化)，回答下列问题。

    In 1986, the Honda automotive company wanted to see if it could make a human-like robot, to help in home, play football, balance on one foot, and even dance. Over the years there were some problems but soon the researchers managed to get a robot named ASIMO. It could walk on uneven(不平坦的) surfaces, and move its center of gravity like we do to climb stairs.

    More recently, ASIMO was improved so it could turn round and run at six kilometers per hour, using its upper body to control movement.

    ASIMO is designed to be friendly. It is hoped that robots like this could be used to help elderly people in their home. Honda are also using this technology to help people with disabilities. It can also push a cart(手推车) and open and close doors. ASIMO can even shake hands. It stands 120 centimeters tall, so that it can look into adult faces when they are sitting down. It can hold two kilos in its hands. It can even carry a tray without dropping the contents.

    So, where next for this kind of robot? Well, while ASIMO is attractive, it is still controlled by a human. Researchers in the USA are working on the robots that can learn about the world around them, and give a reply to human touch and voice. The robots are even learning to recognize(辨认) objects, people and vocabulary. Soon the descendants(后代) of these robots may be serving you drinks or helping with jobs at home and at work.