Every month, Julia and her cousins would go for the big family meal at their grandparents' house. On each visit, their grandpa would give them a few coins. Then all the children would run off to buy sweets. One day, he gathered the children together. He said, "Let's have a competition to see who can manage money wisely. At the end of this year, tell me how you've used your money. "

Ruben and Nico, the two smallest kids, continued spending their money all on sweets. Every time, they would show off their sweets in front of the other children. This made Clara and Joe so angry that these two could no longer keep saving their money. They soon joined Ruben and Nico.

Monty was a clever boy. He decided to manage his money by buying and selling things. Soon he made a lot of money with little effort. The way he was going, he would end up almost a rich man. However, he began to spend his money on more and more expensive things for himself. A few months later, he hadn't a single penny （便士）left.

Alex saved and saved all the coins he was given, and at the end of the year he had collected more money than anyone. He was the clear winner.

There was also Julia. Poor Julia hadn't a penny on the day of the competition. She had spent all her coins on her secret plan. Julia knew a poor violinist who played in the park, and she offered him all the coins for his violin lessons. Although it wasn't much money, on seeing Julia's excitement, the violinist agreed. A little after a year the violinist loaned her a violin so they two could play together in the park. They were so successful that she managed to buy her own violin. Even better, she later became a very famous violinist.

A tree has roots. People have roots too. If you get to the root of a problem, you will solve it. It's the same thing with words. Dig deeply into a big, unfamiliar word and you will understand where it came from.

As readers, especially those reading in a second language, we need to deal with the text as if we were detectives (侦探) looking for information to unlock the unknown. Like any good detective arriving on the crime scene, the first thing to do when meeting a new and difficult word is to judge the situation, to look at everything that is known and see if it helps us to understand what it means.

As you know, prefixes （前缀）and suffixes（后缀） can be added to the beginning or end of words to change the meaning. Know them, and you will have the word building power. But root words are the key. Take time to learn a few of these, put them in your memory, and you will become a master word detective.

Let's look at one common root word used in English. "Alter" from the Latin word means "other". When you meet this root word, you know that the bigger word has something to do with "other". Examine the word "alternate". Can you find the Latin root in it?

Learn as many root words as possible in the language you are studying. Then use your "rooting for words" skills. Like any new skill, practice and hard work are always paid back.

温馨提示：只要有大小写、单词拼写、语法等错误，均不给分。

What color is a tennis ball? Ask your classmates, and they might give you some  answers.

The Atlantic asked 30, 000 people this question. Among the people surveyed, 52 percent said tennis balls are green, 42 percent said yellow, and 6 percent said  else.

According to the International Tennis Federation, tennis balls  yellow. So, why do most people say that they're green?

When we  see an object in natural light, our brains recognize its true color. Even if the object in different kinds of light later, our brains can still tell its true color.  call this color constancy (色彩恒常性). For example, we know that China's flag is red. When we see it during sunset or under purple light, we still know that it is red, even if it looks like a different color.

However, the color of a tennis ball is not as pure (纯的) as the flag. It appears to be a mixture of yellow, a "warm" color, and green, a "cool" color.

The US-based magazine says that when  brains try to figure out what color the ball is, some people ignore (忽略) cool colors like green, blue and purple. So they see the ball as yellow.  ignore warm colors, such as red, yellow and orange. They see the ball as green.

It is not just tennis balls that make such confusion. In 2015, a girl  a picture of a dress online. Some people said the dress was black and blue  other people said it was gold and white. They had different opinions based on whether they ignored cool or warm colors.