铬(Cr)为不锈钢主要的添加元素，含量一般在12％以上。铬的表面生成一薄层致密的钝态氧化物保护膜是不锈钢具有耐蚀性主要原因。请回答下列问题：
(1) 铁生锈的主要条件是铁与____ 和____ 直接接触。
(2) 不锈钢是一种____ （填“合金”或“金属”）。
(3) 相同温度下，取大小相同、表面光亮的Cr、Mg、Cu三种金属薄片，分别投入等体积等溶质质量分数的足量稀盐酸中（反应中Cr显+2价），现象如下：

① 上述三种金属的活动性由强到弱的顺序是____ 。
② 从上述探究实验可知，Cr____ （填“能”或“不能”）跟硫酸铜溶液反应。若反应，请写出反应的化学方程式____ 。

豌豆叶肉细胞中的核酸，含有的碱基种类是 （   ）

When I was young，my father told me that little acts of kindness may give one great happiness. Since then I have always tried to help people in1.
One hot summer afternoon, I was2down the highway to New York when another car suddenly3into my lane(车道). My car was in the far right lane，so it ran onto the roadside. As a(n) 4driver，I moved my car quickly and skillfully back onto the highway without causing any accident.
I was5with that driver，but I thought that he just did not pay attention to the lane change, and he 6did not do that on purpose(故意).The car ran away7after cutting me off. Very soon it disappeared from sight. After a while，I came around a curve(弯道) and found the8car. The driver was walking along the roadside. He was an elderly man and looked9. With no telephone nearby and the nearest services twenty miles away. I decided to 10and see what the problem was.
The man’s car had a flat tire(瘪胎). Although he had a spare tire，he had nothing to work with. I decided to11him. I changed the tire for him and allowed him to sit in my Air-conditioned car while I did it. Fifteen minutes later，I12the work. I was hot and tired，but I really felt13after an act of kindness to the man who had earlier14my car ran off the road.
You can really enjoy great15from kindness acts, so always lend your hands to others in trouble.

11×11=   21×31=

41×31=   51×51=

你发现什么规律了吗？用所发现的规律直接写出下面各题的得数．

21×21=   61×81=   91×31=

31×51=   41×41=   71×51=