现有下列物质：①新制氯水  ②铜   ③稀硫酸

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.

动脑学物理，越学越聪明．小武同学看到商贩将水量浸泡在某种红色液体中，他悄悄地取些样品测量其密度，如图所示，步骤如下：

①用一根两端开口的玻璃管，将其一端扎上橡皮薄膜；

②将玻璃管扎有薄膜的一端逐渐放入装有水的容器中适当位置，并用铁架台和试管夹固定；

③往玻璃管内缓慢地加入样品直到薄膜变平为止；

④对相关的物理量进行测量并计算样品的密度．

根据上述实验，请你回答下列问题：

____(tell) many times, he still repeated the same mistakes.

已知 $\overrightarrow{m}$ ， $\overrightarrow{n}$ 为两个非零向量，且| $\overrightarrow{m}$ |=2，| $\overrightarrow{m}$ +2 $\overrightarrow{n}$ |=2，则| $\overrightarrow{n}$ |+|2 $\overrightarrow{m}$ + $\overrightarrow{n}$ |的最大值为（   ）