被称为元代前期历史剧代表作的作品是（）。 A.《单刀会》和《汉宫秋》 B.《赵氏孤儿

108×23+3672÷18．

恐龙专家：一些古生物学家声称鸟类是一群叫做厥姆恐龙的后裔。他们通过化石记录发现鸟类和大多数的恐龙相比，厥姆恐龙具有的特征与鸟类更为相似。但是，他们的论述存在致命的缺点——已发现的最早的鸟类的化石比最古老的已知厥姆恐龙的化石早几千万年。因此，古生物学家的声明是错误的。
该恐龙专家的论述依赖于下面哪条假设

A．具有相似的特征是不同类型的生物在进化上相联系的标志。

B．厥姆恐龙和鸟类可能会有共同的祖先。

C．厥姆恐龙化石和早期鸟类化石的知识是完整的。

D．已发现的化石揭示了鸟类和厥姆恐龙起源的相对日期。

阅读理解。

     Deputy Agriculture Secretary Kathleen Merrigan sees an epidemic (流行病) sweeping across

     America's farmland. It has little to do with the usual challenges, such as flood, rising fuel prices

and crop-eating insects. The country's farmers are getting older, and there are fewer people standing in

line to take their place. National agricultural census (普查) figures show that the fastest-growing group of

farmers is the part over 65. Merrigan is afraid the average age will be even higher when the 2012 statistics are completed.

     Merrigan, a former college professor, is making stops at universities across the country in hopes of

encouraging more students to think about careers in agriculture. Aside from trying to stop the graying of

America's farmers, her work is made tougher by a recent blog posting that put agriculture at No. 1 on a

list of "useless" college degrees. Top federal agriculture officials are talking about the posting, and it has

the attention of agricultural organizations across the country.

     "There couldn't be anything that's more incorrect," Merrigan said. "We know that there aren't enough

qualified graduates to fill the jobs that are out there in American agriculture."

     In addition, a growing world population that some experts predict will require 70% more food

production by 2050, she said.

     "I truly believe we're at a golden age of agriculture. Global demand is at an all-time record

high, and global supplies are at all-time record lows," said Matt Rush, director of the Texas Farm

     Bureau. "Production costs are going to be valuable enough that younger people are going to have the

opportunity to be involved in agriculture."

     The Department of Agriculture has programs aimed at developing more farmers and at increasing

interest in locally grown food. The National Young Farmers' Coalition has also been pushing for state and

federal policy changes to make it easier for new farmers.

     Ryan Best, president of Future Farmers of America, has been living out of a suitcase, traveling

the country and visiting with high school students about careers in agriculture. The 21-year-old Best

hopes his message-that this is a new time in agriculture-will motivate the next generation to turn

around the statistics. "Never before have we had the innovations (创新) in technology which have

led to agriculture in this country being the most efficient it has ever been," he said. "There's really a place

for everybody to fit in."

1. What is the new challenge to American agriculture?

A. Fewer and older farmers.    

B. Higher fuel prices.

C. More natural disasters.      

D. Lower agricultural output.

2. Why is Merrigan visiting universities across the country?

A. To draw federal agriculture officials' attention.

B. To select qualified agriculture graduates.

C. To clarify a recent blog posting.

D. To talk more students into farming careers.

3. According to Matt Rush, American agriculture will provide opportunities for younger people

    because__________..

A. the government will cover production costs

B. global food supplies will be even lower

C. investment in agriculture will be profitable

D. America will increase its food export

4. What do the underlined words "to turn around the statistics" in the last paragraph mean?

A. To re-analyze the result of the national census.

B. To increase agricultural production.

C. To bring down the average age of farmers.

D. To invest more in agriculture.

确定等同特征时，应当考虑哪些因素？

使用千斤顶时应遵守的规程？