Before the invention of paper，stone，bamboo，wood and silk were used for recording and remembering things．However，there were many difficulties in using the materials for writing．The stone was heavy．The silk was too （1）

expensive

expensive

（昂貴的）to use．Bamboo and wood took up a large （2）

amount

amount

（量）of space．
   So there was a great need for a cheap and easy way to write．After lots of （3）

research

research

（研究）and practice，paper was invented to （4）

replace

replace

（取代）other materials．According to Chinese history，Cai Lun invented paper over 1，900 years ago．
   In the beginning，paper was （5）

mainly

mainly

（主要地）used for recording important events．Paper also helped （6）

spread

spread

（傳播）knowledge．With cheap paper，great and new ideas could be passed quickly and widely．Later，with the （7）

development

development

（發(fā)展）of technology，paper was also used in many other ways．For example，paper was made into fans and umbrellas．In Japan，the walls of homes were often made of rice paper（宣紙）．Nowadays，although we use （8）

electronic

electronic

（電子的）equipment，such as computers and mobile phones，paper is still around us-（9）

textbooks

textbooks

（教科書(shū)），shopping bags，paper money，toilet paper，etc．We use paper in many ways every day．Paper is truly one of the most （10）

powerful

powerful

（有影響力的）inventions of all time．