SECTION C

Directions: Complete the following passage by filling in each blank with ONE word that best fits the context.

How much paper do you use every year? Probably you can’t answer this question quickly. In 1900,the world’s use of paper was about one kilogram  48  each person in a year. Now some countries use as  49 as 50 kilograms of paper for each person in a year. The amount of paper a country uses shows how far advanced the country is, some people say. It is difficult to say  50  this is true: different people mean different things  51  the word “advanced”. But countries like the United States, England and Sweden certainly use    52   paper than other countries.

Paper, like many other things that we use today, was first made in China. In Egypt and the West, paper was not very commonly used before   53  year 1400.The 54  wrote on papyrus; Europeans used parchment for many hundreds of years. Parchment was very strong ;   55  was made from the skin of a certain young animal. We have learnt some of the most important facts of European history from record that were kept on parchment.

（2010）一平面简谐波在弹性媒质中传播时，某一时刻在传播方向上一质元恰好处在负的最大位移处，则它的：（）

A.动能为零，势能最大

B.动能为零，势能为零

C.动能最大，势能最大

D.动能最大，势能为零