The college entrance examination is just around the corner. Homework and tests will keep many of you up late at night, and you may plan to make up for your lost sleep during the weekends. {#blank#}1{#/blank#} is it useful? A study published in the journal Current Biology completely has changed {#blank#}2{#/blank#} people used to think. It shows that the habit of sleeping in on weekends doesn't fix the damage done by a lack of sleep during the week. Even {#blank#}3{#/blank#} (bad), it may damage your health.

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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.

Lily loved school. However, there was one class Lily worried about more than any other—art. She didn't know why she just wasn't any good at drawing, painting, or cutting.

Ms. Clay, the art teacher, stood at the front of the room. "Class, next Friday our school is going to have an art competition," she announced. Ms. Clay was a great teacher, and Lily liked her a lot. But this announcement made Lily nervous. "Everyone in the school will create a piece of artwork to show in the library. You can use the different types of artwork we have been studying." Ms. Clay was quite excited when she spoke while Lily found herself sinking lower in her chair.

Lily had the whole weekend to work on her project, but she could not think of anything to do. On Monday, Lily felt frightened, so after school Lily asked Ms. Clay if she could write an art paper instead of doing an art project.

"I understand this project scared you, Lily," Ms. Clay said. "Just remember, you can create any kind of art you want." Ms. Clay smiled at her. "Art is a person's way of expressing his or her feelings—it isn't always painting, drawing, or cutting. I know you will think of something very creative, and I can't wait to see it."

When Lily arrived home, she took out a piece of paper and a pencil. She remembered Ms. Clay's words. "Art is a person's way of expressing his or her feelings." Lily wrote the word "terrified" on her paper. She crumpled (揉皱) the paper and threw it to the side of her desk.

Then Lily stared at the crumpled ball. Suddenly an idea struck her.

Paragraph 1：

Why not create something out of crumpled paper?

Paragraph 2：

On Friday, Lily carefully carried her project into the library.

It was a typical weekend for Mitch White and his friends. They were out celebrating a bachelor party, sailing the peaceful waters of the Minnesota River. They never expected that this single party would transform from a relaxed canoe trip into a painful rescue mission. With the sun setting, an unexpected bark changed everything.

Led by Mitch White, the soon-to-be-married man, they searched for the source of the sound along the banks of the river. Suddenly, a weak cry for help came from the mud. They were surprised to find that the head of a 13-year-old St. Bernard named Ed was barely visible in the thick mud. Mitch said, "The dog wasn't moving on its own, so we should feed it and give it water. " The dog looked like i had used all its strength.

The men took up their oars（桨） and began digging, their festive mood giving way to a focused rescue mission. It took them more than half an hour to free the trapped dog as it was already breathing very feebly after possibly being trapped for 24 hours. When they got the poor fellow out of the mud, he couldn't walk, so they carried him back to the house. Back home with his owner, George Niskanen, Ed began his slow restoration-a happy ending to a dangerous adventure. George was thankful to the bachelor party heroes.

Now, the people of Carver, Minnesota, have new heroes to cheer for. Indeed, this incredible act of bravery and compassion redefined the meaning of a bachelor party. It became a heroic tale of humanity, friendship, and the instinct（本能）to do what's right.