Question: More and more birds are flying to settle at Qinghai Lake, one of the highest inland lakes in China, thanks to the protection efforts of local governments. Covering an area of over 4,000 square kilometers, Qinghai Lake is also the country's biggest salt-water lake. Located in Northwest China's Qinghai Province, the lake is famous for the two islands at its northwest point--Cormorant Island and Egg Island. The two islands have plenty of floating grass and various schools of fish, offering rich food sources for birds. The islands have become a paradise for different kinds of groups of birds and have been called 'Bird Islands'. Each March and April, when ice and snow covering the Qinghai-Tibet Plateau starts to melt, over 20 kinds of birds fly to the Bird Islands to lay eggs. During the months, flocks of birds cover the whole sky over the islands and birds eggs can be found everywhere. Visitors can hear the singing of birds from miles away. These have become a world famous symbol of the lake. To protect this paradise for birds and support calls for ecological protection, China set up the Qinghai Lake Natural Protection Zone at the end of 1997. Meanwhile, the State has pointed out the Bird Islands and Spring Bay of the Qinghai Lake as central protection zones. Inspection officials and management employees often patrol the lake, improving local residents' knowledge of related laws and spreading knowledge about animal protection to visitors. They are making great efforts to call on people to love and protect the birds. At the same time, they have built special fences around the island area, to prevent wolves, foxes and other carnivorous animals, as well as illegal hunters from breaking up the birds' nest-building, egg-laying and breeding. As a result, more and more birds are coming to the islands for sheltering and breeding. Why are more and more birds coming to the biggest salt-water lake in the Great Northwest? A) Because it is getting warmer and warmer. B) Because it is being reformed C) Because environments there are getting more and more agreeable for them to live in. D) Because the people there are becoming richer and richer
Answer:
C