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With the completion of the Human Genome（基因组）Project more than 20 years ago, and the discovery of the double helix structure of DNA enjoying its 70th birthday last year, you might assume that we know how life works. Think again!

Evolution has a 4bn-year head start on us. However, several aspects of the standard picture of how life works-the idea of the genome as a blueprint, of genes as instructions for building an organism, of proteins as precisely tailored molecular（分子）machines and more-have wildly reduced the complexity of life. 

In the excellent book How Life Works, Philip Ball explorers the new biology, revealing life to be a far richer, more delicate affair than we have understood. Ball explains that life is a system of many levels-genes, proteins, cells, tissues, and body modules-each with its own rules and principles, so there is no unique place to look for an answer to it. 

Also, How Life Works is a much more appealing title than the overused question of "What is life?". We should be less concerned with what a thing is, and rather more focused on what a thing does. Defining a living thing implies an unchangeable ideal type, but this will run counter to the Darwinian principle that living things are four-dimensional, ever changing in time as well as space.

But it's an idea that is deeply rooted within our culture. Ball points out that we rely on metaphors（比喻）to explain and explore the complexities of life, but none suffice. We are taught that cells are machines, though no machine we have invented behaves like the simplest cell; that DNA is a code or a blueprint, though it is neither; that the brain is a computer, though no computer behaves like a brain at all.

Ball is a terrific writer, pumping out books on incredibly diverse subjects. There's a wealth of well-researched information in here, and some details that are a bit chewy for the lay reader. But the book serves as an essential introduction on our never-ending quest to understand life.

One teacher had two students. One of them had a positive vision while the other had the 1 one.

One day, the teacher 2 for a park with both the students and while wandering in the garden, they 3 a mango tree from which some ripe and juicy mangoes were 4 . On seeing this, the teacher thought to 5 both of his students. Then, he asked the first one, "My dear child, what do you think of this mango tree?"

The student answered instantly, "Teacher, in spite of people 6 this tree with stones, it gives us sweet and juicy mangoes. It does 7 but still it gives us fruits. I wish all human beings learn this important 8 from the mango tree-to share their 9 even if they have to suffer for this."

After that, the teacher asked the other student the same question. The student 10 answered, "Teacher, this mango tree is no good and will not give mangoes by itself but only when we hit it with stones and 11 . Therefore, we should hit it hard to get sweet mangoes from it. That is the only way to 12 these mangoes. It is also clear from this tree that in order to get good 13 from others, we need to be violent and only when we become violent, then and only then will we get 14 ."

The teacher was delighted with the answer given by the first student because he had an admirable vision and 15 the tree with positive vision.

The popularity of ancient towns in the south of the Yangtze River, such as Zhouzhuang and Wuzhen, has aroused a nationwide trend in the construction of ancient towns. Lin Peng, the director of China's Institute of Ancient Cities and Cultural Studies, pointed {#blank#}1{#/blank#} that there are more than 2,800 developed or developing ancient towns in our country, {#blank#}2{#/blank#} is definitely the highest number globally.

In ancient towns, {#blank#}3{#/blank#} immersive（沉浸式） experience being mentioned here is historical and cultural characteristics—the "ancient" of ancient towns. Apart from visible "special buildings", characteristics also include invisible "culture". Tourists in ancient towns want to see the living {#blank#}4{#/blank#} （condition） of local people, feel the vitality of town life, try characteristic local snacks {#blank#}5{#/blank#} （influence） by geography and folk customs, and understand how long history {#blank#}6{#/blank#} （shape） local culture. Out of modern fast-paced work and life, tourists want to awaken their inner softness with a slow-moving ancient town.

Touring ancient towns is for recreation, relaxation, and pleasure, {#blank#}7{#/blank#} if all the ancient towns in different places are the same and cannot find their own {#blank#}8{#/blank#} （unique）, then ancient town tourism will {#blank#}9{#/blank#} （eventual） decline. Let every ancient town become a unique historical imprint（印记）, so that tourists can find their "poetry and distance" while {#blank#}10{#/blank#} （wander） through the ancient towns. This is the soul that ancient towns need to regain.