After years of research and tests, the hybrid car was developed and put on the market. It's an interesting and exciting new improvement in today's world as we look for better ways to protect the quality of the air we breathe and protect our natural resources.

The quality of our air is affected by many different things. But one of the largest sources of air pollution is the burning of fossil fuel such as coal and gasoline which is used to power a car's engine. The Environmental Protection Agency（EPA）has set national standards to help control the level of harmful pollutants sent off into the air, and the automobile industry has acted by producing the hybrid car that uses less gas and therefore causes less pollution.

A hybrid car is a combination of a regular car that runs on gasoline and an electric car that is battery-powered. Some people tend to think that since the hybrid car is partially electric, you have to plug it in to charge it. But that's not how it works. The 144 volt battery pack（电池组）is actually recharged through the energy that is produced when the car's brakes are used. This is referred to as "regenerative braking", because it generates electricity.

Although the hybrid car still runs on gasoline most of the time, this helps it use less gas than a regular car. When the driver stops at a traffic light, the engine automatically shuts off to save fuel. Then, as soon as the driver puts the car in gear and touches the gas pedal（踏板）, the engine starts backing up.

Have you ever ridden in a car with someone which ran out of gas？That probably wouldn't happen if you were riding in a hybrid car. It flashes a warning on its computer screen that says, "I am low on gas. "When it completely runs out, the warning reads, "YOU ARENOW OUT OF GAS！"Then the electric power supply starts to work to let the driver travel a few more miles to a gas station.

   China may be the world’s largest market for e-bikes, but Europe is fast catching up. The EU’s official statistics agency says the figure reached the one million mark two years ago, and sales have sharply increased since then.

When running errands（差事）around Berlin, Lutz, who usually works by horse, uses the company’s new e-bike that is charged easily and has a range of 140 kilometers. “We found there was no parking spot problem or other worries. And on top of all these, we don’t pollute the environment. Petrol is also saved,” said Lutz Baddack, owner of Reitsport Baddack.

Unlike many other parts of the world, the EU does not require registration（登记）of e-bikes. Nearly half a million are expected to be sold in Germany this year, in all shapes and sizes. “It’s not just bike fans buying them. People who usually drive cars also use them occasionally,” said Stefan Gelbhaar.

Businessmen say the elderly are also big customers. The sales of ordinary bicycles fell in Germany last year, but the sales of e-bikes rose by 8 percent. Sales figures are expected to keep going up. “In five years we will have the market share of 20 percent, or maybe more,” said Marcus Kendler, owner of E-Motion. In the hillier parts, that figure has already been beyond it.

The sales of e-bikes in Germany have been much larger than those in any other country in Europe. But other countries are fast catching up. In Europe, with the various brands at the market and falling prices, e-bikes are here to stay and not just a repeated trend.

   With an improved economy，many travelers have been buying first or business class seats，leaving fewer for upgrades（升级）.Here are some strategies for getting a free upgrade.

1. Fly a lot.

This is the most common way to earn a free upgrade. Most airlines reserve some spaces for travelers who fly at least 5，000 miles per year. Five years ago，this meant half or more of domestic（国内的）first class travelers sat up front for free. But now，airlines are selling more high-price seats，so on popular routes it is not unusual for more than 20 travelers to compete for one or two upgrades. But on routes with fewer business class travelers，free upgrades remain more plentiful.

2. Use miles.

If you're not a frequent traveler but still have some miles to fly，you may be able to use them for an upgrade. Be careful，though，as many airlines now ask not just for miles but also a cash co-pay. One example: on flights to Europe，American Airlines charges 5，000 miles，plus $110，for a one-way upgrade from discounted economy class to business class. For most domestic upgrades，American Airlines wants 15，000 miles plus $ 75.

3. Get lucky.

Sometimes airlines overbook coach（经济舱），and a few travelers get no seats. Agents try to ensure the airline's most loyal travelers get the nod（被选中）. Agents usually have some flexibility to make sure the plane is full and takes off on time. So it's the easiest way for them to do it-they might upgrade someone else out of order.

4. Save a life.

Flight attendants don't usually upgrade passengers, even when empty seats remain. Doctors and nurses who answer an emergency call are sometimes an exception. If they comfort a passenger, flight attendants might allow them to sit in business or first class for the rest of the flight.

   Sometimes you have to visit your friends or relatives without much time for making preparations. Your only problem seems to be what to do with your pet. You can either leave it at your home or bring it with you. Traveling with your pet is easier than you think.

You can bring your pet with you by using air travel services. These services fall into two groups, in a cabin（客舱）and cargo. In-cabin pets must be small enough to fit into a carrier that will be placed under the seat in front of you. Pets too large to fit comfortably into a carrier must travel in a cargo. Cargo holds are heated or cooled, just like the passenger area.

Pet passengers require a reservation（预约）, whether traveling in a cabin or cargo. Airlines have rules about the number of pets they will carry in order to ensure travel safety for all. So making your pet's reservation as you buy your ticket is a good idea. Of course, you should pay extra charges for both in-cabin and in-cargo pets.

Buy a health certificate from your vet（兽医）. A health certificate is only good for ten days, so if your visit is longer than that, you will have to buy another health certificate for the return trip.

As mentioned, your in-cabin pet will need a carrier. These soft-sided carriers come in several sizes, so buy or borrow one that allows your pet plenty of room. Some of these can be bought with wheels to make transport through the airport easier; these also reduce "pet space" under the airplane seat. But pets traveling in a cargo need hard-sided carriers.