Because of the development of agriculture, the area of land affected by sand has gradually increased. During the 1950s and 1960s the land affected by sand expanded on average into 1,600 square kilometers per year. By the 1990s, the area had reached 2,500 square kilometers per year. This kind of situation is particularly serious in many regions upwind(逆风的) from Beijing. Fengning City in Hebei Province and Duolun City in Inner Mongolia lie to the north of Beijing, and in the last 50 years the population of these two cities has grown by 2 to 3 times. In order to obtain more resources, the inhabitants have been busy with heavy farming, tree-cutting and keeping animals. The result is that the soil which has sustained damage, and the sand layer below the earth is now exposed on the ground and the ground is rapidly being controlled by the spread of sand. China has already noticed this problem, and has take measures to save the land. Nowadays, some land used for farming has returned to forestland and grassland. The Chinese government announced that it would invest more than RMB 600,000,000 to control Beijing’s sandstorms in the coming years. Only by decreasing the damage caused by man and restoring the natural environment will it be possible to well control the sources of the sand and dust. We hope in the not-distant future, we will solve the problem successfully and effectively. 63. Compared with 50s and 60s, the land affected by sand increased by _____ square kilometers by the 1990s. A. 1,600 B. 2,500 C. 900 D. 1,100 . Which of the following is NOT the cause of the damaged land? A.People use the resources too much. B.People keep animals which need more grain. C.People prepare too much land to grow crops. D.People cut a lot of forests and raise animals. 65. The major measure that Chinese government has taken is _____. A.controlling the growth of the population B. better use of natural resources C. killing fewer animals and cutting fewer trees D. returning some land to forestland and grassland 66.According to the passage, it can be inferred that _____ was the major factor of the environmental damage. A. man B. animal C. nature D. desert