【推荐1】If you go out to the fields at night spring or summer, you can hear singing    1    (happy)here and there. It seems as if they were performing a field concert.

The frog is a beneficial creature that does good to human beings. They can catch fast-moving insects. Each frog eats a large number of pets that are harmful to crops. This little creature is regarded     2    the natural enemy of pests.

But now the number or frogs    3    (become)smaller and smaller. This is    4    they are killed and put    5    the table as a delicious dish by their chief enemy, human beings. It is cruel, isn’t it? The cause of the rapid    6    (reduce)of frogs is that farmers use pesticide(杀虫剂)to kill pests ,and then frogs get     7    (kill)as a result of eating the poison-killed insects.

Something must be done without delay    8    (save)frogs. If we don’t punish those     9    sell and kill frogs to make money, then one day all of us     10    (punish)by nature for failing to save frogs.

Last year I spent a day on the plain in Tibet observing Tibetan antelopes .     1     (watch) them move slowly across the green grass, I     2     ( strike) by their beauty. I was also reminded     3     the danger they were in. The 1980s and 1990s were bad times for Tibetan antelopes. They were being hunted     4     (illegal) for their valuable fur     5     the number dropped rapidly. In order to save this species from extinction, the Chinese government has taken some     6    (effect) measures and much     7     ( do) by the volunteers in the past few years. Now the antelope population has recoverd and the Tibetan antelope has been removed from     8     endangered species list. The government,     9     , does not intend to stop the protection programmes, since the     10     (threat) to the Tibetan antelope have not yet disappeared.

Every autumn, millions of the North American monarch butterflies begin a long and difficult journey. Somehow they manage to travel around 4,000 kilometres south and find their way to California or Mexico. However, until recently no one     1     (know) how they did this.

A team of scientists     2     (lead) by Professor Eli Shlizerman has now found the answer. They have found out that the monarch is able to tell the time of day. It uses its eyes     3     (measure) the position of the sun. These two pieces of information allow the butterfly     4     (determine) the way to go. Finally, it manages to reach the places where it will spend the winter.

    5     (sad), human activity is the main reason     6     the number of monarch butterflies is falling. In many of the places where the butterfly can be found, people are destroying the     7     (nature) environment. They cut     8     trees and use chemicals that kill the plants that monarch caterpillars eat.

The research on the monarch’s behaviour has however led to a greater     9     (aware) of this creature. People have been working together to record its migration and make sure that there are enough plants for it to feed on. If this works, there may come a time when     10     number of monarch butterflies increases once again.

The silent killer — air pollution causes seven million premature (过早的)     1     (death) a year, not just in     2     (develop) countries but also in UK and the USA as well. In China，people are well aware of the health problems it brings.

I check every part every day. If it has heavy air pollution, I will prepare masks for my family. I dislike     3     when the air is bad. Because bad air makes it difficult for me to breathe and I think it does influence my     4     (perform) at work. A new research in china has also found a link between air quality and levels of intelligence. In the study, 25,000 people living across China     5     (test) in language and math skills last year. They found the results of those     6     lived in more polluted areas were     7     (negative) impacted, especially in languages. It adds to a growing body of evidence that air pollution has an effect not just on the lungs and heart     8     on the brain.

This research shows that the longer we are exposed to air pollution, the     9     (many) problems we’re storing up for later life. Campaigners hope this study will persuade the British government     10     (think) hard before it publishes its clean air strategy next year.