Forests have always been important to people. We make use of them in many   46  . First, trees   47   man fruits and building materials in the form of wood. Without trees it would be   __48   to build houses, boats, bridges and so on. Furniture such as desks, chairs and beds are made of   49  . Second, trees can  50   man from terrible heat. They provide shade for us. Third, they are also useful in stopping rich top soil from being washed away by heavy rains. The top soil is   51   for plants.

Unfortunately, because people in the past did not know enough about the science of nature, they   52    down too many trees and never planted new ones. Gradually the   53   of trees became smaller and smaller. And the rich surface soil was blown and washed away by strong wind and heavy rain. In the end the rich lands    54   into useless deserts.   55__  could grow there any more.

(   )46. A. ideas                B. ways                 C. parts               D. countries

(   )47. A. give                 B. show                C. make              D. bring

(   )48. A. different             B. impossible      C. interesting         D. easy

(   )49. A. plastic                      B. glass                 C. rubber             D. wood

(   )50. A. separate             B. stop            C. protect         D. save

(   )51. A. bad                  B. dangerous       C. important        D. special

(   )52. A. wrote               B. cut                    C. broke              D. pulled

(   )53. A. number                     B. height           C. weight            D. quality

(   )54. A. flowed               B. ran                    C. changed            D. fell

(   )55. A. Everything          B. Something     C. Anything           D. Nothing