Around       1     earth, there is a thin layer of ozone(臭氧), a kind of gas protecting us from any of the harmful rays of the sun. A few years ago, scientists in the Antarctic became aware     2     holes growing in the ozone layer. As these holes get bigger, harmful rays from the sun are     3     (increasing) reaching us,     4    (cause) crop damage and cancer. This is a big problem in countries near the polar regions, like Australia     5     skin cancer caused in part by ozone depletion (消耗)is now considered a national epidemic(流行病).

Further research into the problem showed that the ozone layer is being destroyed by gases called CFCs. These gases     6     (release) into the atmosphere by the chemicals used in aerosol cans, refrigerators and air conditioners. To help save the ozone layer, many     7     (manufacturer) have stopped producing aerosol cans that use CFCs. They have switched to other less harmful chemicals, and labeled     8     (they) cans “ozone-friendly” or “no CFCs”.

The problem of refrigerators and air conditioners has been more difficult     9     (solve). However, more and more manufacturers are now producing refrigerators and air conditioners     10     do not use CFCs. Therefore, when you go shopping you should choose ozone-friendly products. Then you will be doing something to help the environment.

Global warming refers to the fact that the earth's atmosphere is warming near     1     (it) surface — in other words, it's getting hotter. Some scientists say it is human activity     2     has caused global warming. However, there are other theories as well.

One popular theory relates to the “greenhouse effect”. Gases that make up the atmosphere are similar to     3     greenhouse because they allow sunlight     4     (pass) through, and then trap much of the heat from     5     (escape). This naturally occurring phenomenon,     6     is called greenhouse warming, keeps the earth's surface     7     (warm) than it would be.

While scientists agree that human-produced compounds (化合物) like carbon dioxide and others are being released into the atmosphere, some argue it's not clear how this results     8     the changes in temperature.

Global warming can     9     (great) affect human life on many levels. Scientists have made great     10     (contribute) to finding out how long the earth has been warming, at what rate it is warming, and what factors are causing it. These answers may better prepare people to handle its effects.

Ecotourism is commonly regarded as low impact (影响) travel to undisturbed places. It is different from traditional tourism because it allows the traveler to become     1     (educate) about the areas - both in terms of geographical conditions and cultural characteristics, and often provides money for conservation and benefits the     2    (develop) of the local areas.

Ecotourism has     3    (it) origin with the environmental movement of the 1970s. It was not widely accepted as a travel concept     4     the late 1980s. During that time, increasing environmental awareness made it desirable.

Due to     5     growing popularity of environmentally-related and adventure travel, various types     6     trips are now being classified as ecotourism. Actually, a true eco-friendly trip must meet the following principles:

·Minimize the impact of     7    (visit) the place.

·Build respect for and awareness of the environment and cultural practices.

·Provide     8    (finance) aid and other benefits for local peoples.

·Make sure that the tourism provides experiences for both the visitors and the hosts.

Komodo National Park, officially recognized in 1980, is popular for ecotourism because of its unique biodiversity.    9    (activity) there range from whale watching to hiking (远足) and accommodations aim     10    (have) a low impact on the natural environment.