3 . When water is cold, people will find it uncomfortable to swim. Wetsuits(潜水服）can help keep people warm.    1    So wetsuits are important. In many water sports, you can find people wearing them.

The wetsuit doesn't have a long history. According to studies, the wetsuit only began during WWII when Italians started wearing wetsuits that were made of rubber. And it was widely believed in 1951, Hugh Bradner began working to improve the equipment.     2    

Now there are many kinds of wetsuits. Contrary to what some may think, wetsuits do not work by keeping the diver(潜水员）dry; they are designed to let water into the suit. This thin layer of water is trapped（保存）between the diver and the suit. And it's allowed to move between the skin of the diver and the inside layer.     3    And it can help keep the diver comfortable during the diving process. That's why it's important to have a nice, tight fit for a wetsuit.

    4    The shorter wetsuit often provides cover for the main part of people's bodies. This kind of wetsuit works well with boating, water skiing, swimming, etc. A longer wetsuit can completely cover the body, including long legs.With more protection for the body, it may be used in cool weather conditions.

Wetsuits can also differ in thickness. They range from about 0. 5mm to 8mm in thickness. It's true that thicker wetsuits are more likely to affect your movement.     5    Generally, the colder the water you plan to dive in, the thicker the wetsuit should be.

5 . When I was a practice teacher in a middle school，the students in my class were always making ______，and had no interest in chemistry. So I decided to do ______to change their______ towards chemistry.

The evening before I would teach all by myself，I gave a piece of paper to everyone. I told them to write ______ they wanted on the paper and handed it in and then I could tell what each one had ______ .All the students said I _____ be longsighted(远视)．Then I stood ______ my back towards them. I didn't turn back ______ they had finished and ______ all the paper in a cardboard case.

I turned the cardboard case with the bottom(底部)towards the students，and told them calmly what each one had written on the paper. The students were surprised，______ that I had learned their ______ completely in such a short time.

I told them the truth and they were ______ at my brightness：there were five lines of students in the classroom，and every line had ten students. I had written serial number(from 1 to 50 )on every ______ of the paper in a chemical reagent(试剂)that cannot be seen ______eyes，and then gave ______out to the students according to the groups of their seats. After the paper was ______ in，I used______ chemical reagent onto the corner of the paper. Thus the serial number was ______！

______ ，the students became ______ interested in chemistry，and we became good friends.

When I was a kid, my parents were busy working so they enrolled (登记) me in the Spartak Tennis Club in Moscow. Every day after school my parents would take me to Spartak and I would be there until maybe nine o'clock. All we did was play tennis, eat, do homework, have fun and hang out. It was basically my second family.

In that second family was a woman who was like a mother to me, my first coach, Larissa. I still refer to her as my second mother. She taught me everything I know about how to play tennis, but she’s also a wonderful person. She’s kind and patient, which is not what you expect from one of the top tennis coaches in Russia.

Her program when I was little was based on tricking us into doing our exercises. She would put a candy under the cones (锥形物), and we would try to hit the targets with balls, you got to have an ice cream.

Of course we worked hard and I didn’t let her down.

My second-ever tournament was the Moscow Championships, and I won. Afterwards Larissa came up to me and said, “Congratulations, Enjoy today because tomorrow it’s back to work.” She was always telling us to celebrate and have fun with any particular achievement but to always remember there is something more you can do, something more you can achieve.

Now every time I go back to Russia I go to Spartak to see Larissa. We look at all the pictures from all the birthday parties and tournament and celebrations. It is really cool to have someone like her in my life. Larissa is still coaching, but we don’t talk much about tennis any more. We just talk.

Facebook founder and CEO Mark Zuckerberg says he will read a book every two weeks, and he’s invited people all around the world to join him.

The “year of books” is Mark Zuckerberg’s 2015 goal. The billionaire is famous for his quirky New Year’s plans. Two years ago, he challenged himself to meet a new person a day. Last year he attempted to write a “thank-you note” every day. He said, “Although I’m very busy, I always have many strange ideas and I still have time to achieve my goals. If you set a goal, you must try your best to make it come true.”

It will come as no surprise that he’s already launched a Facebook page — entitled “A year of books” — to serve as the reading group’s discussion center. Over 62,000 people from all around the world have liked the page in the first 24 hours. Many of them expressed their desires to join Mark Zuckerberg in reading a book every two weeks in their message of the page.

“I hope all the people who participate in the discussion actually have read the books and have relevant points to add. The group will keep it continuously focused,” he stressed on his Facebook page. “With the development of technology, fewer people in the world read books. I do hope people read more books in their spare time rather than surf the Internet or play with their mobiles,” he added on his Facebook page.

The plan is to select books about various topics and cultures. “The Bible” and “Quran” (《可兰经》) have been popular suggestions among hundreds of other titles. The first book is “The End of Power” by Moisés Naím, a former Foreign Policy editor. It’s a 300-page deep dive into the changing nature of leadership today that was published in March 2013.