一个口袋里装有大小相同的6个小球，其中红色、黄色、绿色的球各2个，现从中任意取出3个小球，其中恰有2个小球同颜色的概率是____．若取到红球得1分，取到黄球得2分，取到绿球得3分，记变量ξ为取出的三个小球得分之和，则ξ的期望为____．

【加试题】有如下VB程序段：

Dim a(5) As Integer

Dim i As Integer, j As Integer, t As Integer

a(1) = 52: a(2) = 15: a(3) = 37: a(4) = 22: a(5) = 35

i = 1

Do While i < 5

    t = i: j = i + 1

    Do While j <= 5

        If a(j) > a(t) Then t = j

        j = j + 1

    Loop

    x = a(t): a(t) = a(i): a(i) = x

    i = i + 1

Loop

Text1.Text = Str(a(2))

运行该段代码后，文本框Text1中显示的内容为（   ）

阅读理解
There was a man who had four sons. He wanted his sons to learn to not judge things too quickly. So he sent them each on a quest, in turn, to go and look at a pear tree that was a great distance away. The first son went in the winter, the second in the spring, the third in summer, and the youngest son in the fall.
　　When they had all gone and come back, he called them together to describe what they had seen. The first son said that the tree was ugly, bent, and twisted. The second son said no - it was covered with green buds and full of promise. The third son disagreed, he said it was laden with blossoms that smelled so sweet and looked so beautiful, it was the most graceful thing he had ever seen. The last son disagreed with all of them; he said it was ripe and drooping with fruit, full of life and fulfillment.
　　The man then explained to his sons that they were all right, because they had each seen but one season in the tree's life.
　　He told them that you cannot judge a tree, or a person, by only one season, and that the essence of who they are - and the pleasure, joy, and love that come from that life - can only be measured at the end, when all the seasons are up.
　　If you give up when it's winter, you will miss the promise of your spring, the beauty of your summer, fulfillment of your fall. Don't let the pain of one season destroy the joy of all the rest.

比较是学习历史的重要方法之一，如果将河姆渡原始居民和半坡原始居民进行比较，其中相同点有（  ）
①都使用磨制的工具②都种植了农作物③都是黄河流域原始居民的代表④都出现了原始的畜牧业和农业

化简求值： $\frac{a^2+3a}{a^2+2a+1}÷\frac{a+3}{a+1}-\frac{1}{a+1}$ ，其中a=2．