Polar bears are undergoing hunger in a world     1     (warm) than ever before.

Polar bears live in the environment too cold for most animals. For most of the year, they live and hunt on Arctic sea ice. Nature has prepared     2     (they) for the cold conditions. But nothing has prepared the bears for the danger     3     threatens their only home.

Polar bears’ world is melting. Studies show that polar ice     4     (reduce) by 9.8% every 10 years since 1978. Now about 20,000 to 25,000 polar bears live in the Arctic. Polar bears depend     5     sea ice for their     6     (survive). “Sea ice is more than just the platform that the bears walk over,” says Andrew Derocher,     7     scientist who studies North American polar bear populations. “Without it, they can’t exist.”

    8     (melt) and refreezing of polar ice is natural. But in a warmer world, the cycle speeds up, and polar bears have less time     9     (hunt). Normally, they have three months in the spring when they gain more weight. The extra fat will be used, when the bears are not     10     (active) hunting.

Located in the north-east of Italy, Venice is     1     (know) as “The Floating City”. Water has always been a big part of life in Venice, and even today, they remain the most common way to travel around. Unfortunately, water is also putting Venice     2     great danger. Saltwater is slowly damaging the bases of Venice’s buildings. More problems are caused by floods,    3     usually hit the city each winter.     4     these floods could now be a thing of the past thanks to a new flood prevention project.

Venice     5     (lie) in the middle of a lagoon (泻湖), with three     6     (nature) gaps open to the sea. Rain and strong winds cause seawater to travel through the gaps to Venice. Dozens of gates     7     (build) to hold back the sea in the past few years. Each of these gates is 20 metres wide, with the longest about 30 metres long. In the event of a big rise in the water level, the gates will be raised     8     (separate) the city from the sea.

But only time will tell if this project is the right     9     (solve). The important thing is that action is being taken to protect this unique city for future generations. And if it works, it means a longer and     10     (dry) future for Venice.

To observe Tibetan antelopes, we made a trip to Tibet. There we made out     1    herd of graceful animals. We    2    (strike) by their beauty when watching them across the green grass. However, I was reminded of the danger they are in. They are being hunted    3    (legal) for their valuable fur.

To protect them, the Changtang National Nature Reserve was set up,    4    is a shelter for the animals and plants of northwestern Tibet.

In the 1980s and 1990s, the population dropped badly because of being shot to make profits and the loss of     5    (they) habitats. In order to prevent this species from    6    (extinct), the Chinese government took    7    (effect)measures to place it under national protection. Its population has recovered and it was removed from the    8    (danger) species list in June 2015. But the government didn’t intend    9    (give) up the protection programs. To save wildlife, we should learn to exist    10    harmony with nature.

Northern Kenya is a vast, varied and breathtakingly beautiful landscape    1    you can find the “Towers of the Savanna” — reticulated (网纹的) giraffes. They are one of Africa’s most impressive and popular animals, and yet the    2    (adore) creatures are still little studied and not well understood. However, before we could begin to research into these giraffes, they are being threatened with    3    (extinct).

According to Giraffa camelopardalis reticulata, across Africa, all giraffe populations    4    (decline) by over 70 percent in the past 20 years from 36,000 to less than 9,000 today. The main    5    (element) behind the unpleasant situation appear to be illegal hunting, land degradation (恶化) and lack    6    habitat. The decrease led the IUCN Red List, an authoritative indicator of the health of the world’s biodiversity, to    7    (official) list giraffes as one of the endangered species in December 2016.     8     is now clear that they need conservation efforts.

To better understand the wildlife found here, Wildwatch Kenya seeks    9    (identify) and track the giraffes in conservation field sites. Citizen scientists are called to help researchers look through the tens of thousands of photos taken by cameras    10    (place) in strategic spots throughout the sites.

Last year a storm swept through two villages in the New Territories,     1     (destroy) fourteen homes. Seven others     2     (damage) so badly that their owners had to leave them, and fifteen others had broken windows and     3     (roof). One person was killed and seven were     4     (terrible) hurt. Altogether over two hundred people were homeless after the storm.

Mr. Tan,     5     farmer, said that the storm began early in the morning and lasted for over an hour. “I     6     (eat) with my wife and children when we heard a flood noise.” He said, “A few minutes later our house fell down on top of us. We managed     7     (climb) out but then I saw that one of my children was     8     (lose). I went back inside and found him, safe     9     very frightened.”

Soldiers helped to take people out of the flooded area to the welfare department     10     they could get food, clothes and shelter.

Litter is everywhere，doing great harm     1     the environment and life on our planet.Jeff Kirschner，who wants to build a litter-free world，started a global community named Litterati     2       (settle)this problem.

The story began with his 6-year-old daughter.One day they were going on a hike when the girl noticed a     3     (break)plastic tub(浴盆)in a river.She said，“Daddy，that doesn’t go there.”That took Kirschner by surprise.He，like many adults，had become so used to the rubbish around them that he hadn’t given it a second look.    4     his daughter said reminded him of the serious problem our planet faces.

Jeff started to take       5    (act).He created Litterati，an app that makes it fun to pick up litter.The idea is       6    (fair) simple:Spot a piece of trash，take a photo，post the photo online and then put the litter into dustbins.

    7     (see)that Jeff was keeping a record of the positive impact he was having on the planet，people worldwide started participating.Up to now，over 2，500，000 photos posted by 3,500 people from over 40 countries     8     (find)their way to Litterati’s digital landfill.

Litterati is more than an app.It is a highly     9     (effect)solution to a pressing issue.Wherever you live，whatever you do and       10     you are，join Litterati to make the world a cleaner and healthier place to live in.