3 . 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.

4 . One thing that sets humans apart from other members of the animal kingdom is our tendency to develop customs and traditions. Here are some astonishing customs from around the world.

An odd custom associated with the United States is its complicated tipping culture. Unlike many other countries that don’t tip at all or that only tip in small amounts when the food is particularly good, tipping is actually mandatory at most restaurants in the US. To put it another way, customers have a duty to leave between 10-20 percent of the bill in tips. Wait staff rely on these tips for a living because legal wages for waiters are low. Furthermore, there are rules for tipping bartenders, delivery people and other service personnel. While some criticize this practice as irrational, there’s no doubt that tipping culture in the US gives an incentive for waiters and waitresses to provide better service.

Some countries find the act of pointing with the index finger to be rude. While members of most cultures would probably agree that pointing fingers, both literally and figuratively, isn’t exactly the nicest thing in the world, in countries like Malaysia and Indonesia, this gesture can be seen as incredibly offensive. Instead, it is customary to gesture towards things with the thumb as this is seen as a more polite option. In many countries in Africa, pointing is reserved for inanimate objects only, not people.

Most societies around the world have rules about table manners. For western cultures, noisily consuming food is considered rude. In Japan, however, making slurping(啧啧响的)sounds while eating has an entirely different meaning. This might have something to do with the fact that in western countries, noodles are properly consumed by twirling(缠绕)them on a spoon before putting them in the mouth. Meanwhile, the Japanese simply slurp up their noodles without contorting them first, an act that is naturally noisier than the former. Making slurping sounds when eating noodles in Japan is a way of indicating that you’re rely enjoying them. Some scientists even argue slurping invites air into the mouth and actually enhances the noodles’ flavor.

8 . It was a February afternoon in a Brooklyn classroom. Sixteen-year-old Taylor Engler came face to face with a cow. But it was all in her head. She was transported by a virtual reality (VR) headphone. It took the Berkeley Carroll School junior and eight other classmates to a northern New York farm. The farm was 250 miles away. For students, the technology means field trips are no longer kept within the length of a bus ride.

It's unknown how many classrooms have or will use the technology, but experts say few classrooms do or will do. Headphones that require a user's phone can cost as little as $20 or $30, but systems and software for classes run into thousands of dollars. The problem of not having good software is disappearing as more companies enter the market. But the rules for use haven't kept abreast of the development of the technology. In New York, for example, virtual reality lab experiments are not included in the state's hands-on lab time requirements.

Experts say science classes are where virtual reality holds promise for classrooms. “The biggest problem, I think, is going to be how closely it mimics the real world." That's according to David Evans, the director of the National Science Teachers Union. However, he said, “The ability to do dangerous things and to run many, many more cases in a virtual space as opposed to the real physical space stands for a huge learning chance.”

Lamb taught chemistry and he agreed. “Too often in schools, when you do experiments in labs, you mix these together, you mix those together and you get this result. And if you don't get that result, you have done something wrong. But we don't have enough resources for you to redo it, “he said. “In virtual reality, all I do is hit reset on the computer. I don't have to actually use chemicals.”