下列各句中加线成语的使用，恰当的一项是 A．在国庆节前的全市卫生大扫除中,市直属

关于力的说法中，错误的是（　　）

A．力的作用不是使物体运动

B．力是改变物体运动状态的原因

C．两个物体只有接触才能有相互作用

D．没有物体就不会有力的作用

“Around 500,000 years ago, at the Peking Man Site at Zhoukoudian in Beijing’s suburban Fangshan district, which is about 50 km from the city of Beijing, there lived early human beings,” says a China history textbook.

The textbook now has to be revised. New dating techniques suggest the remains of Peking Man--- found in the 1920s---are over 200,000 years older than previously thought. What’s important about that date, about 770,000 ago, is that this was an ice age on Earth.

Over Earth’s long history, there have been a number of times when ice and snow covered a large part of its surface. Such periods are known as ice ages.

Earth is in an ice age now. It started about 2 million years ago. Despite the many warm periods since then, scientists regard the whole time as one ice age because of the continuous existence of at least one large ice sheet---the one over Antarctica.

The new discovery was made by Chinese and US scientists. It suggests Peking Man is probably our oldest cold weather human being, said Darryl Granger, an atmospheric scientist at Purdue University whose research appears in Thursday’s edition of the journal Nature.

The average yearly temperature at the time in that part of China was around the freezing mark, but it was too dry for an ice sheet, Granger said.

This raises a question. How did Peking Man survive the cold weather?

Rick Potts, a Smithsonian Institution human origins expert who wasn’t involved in the research, raised three possibilities:

First, fire. Early findings showed signs of a fire in Peking Man’s cave. But there has been debate about whether the fire was accidental or controlled.

Second, fur. There is no evidence that Peking Man used simple tools to make more form-fitting clothes, it’s more likely he wore animal fur.

Lastly, he may have developed gradually to handle the cold. Peking Man may have experienced physiological changes that allowed more blood to flow to his hands and legs, Potts said. “People in general who live in colder climates tend to be shorter and wider,” he explained.

Unlike the times of Peking Man today the global temperature is rising due to the greenhouse effect. In the future, could humans develop to handle the warmth just as Peking Man did to fight the cold?

72. According to the new research, Peking Man actually dates back to _______.

A. around 500,000 years ago            B. over 200,000 years

C. about 770,000 years ago             D. about 2 million years ago

73. What is the most important standard for scientists to decide an ice age?

A. The weather conditions.              B. The continuous existence of any large ice sheets.

C. The average yearly temperature        D. The long period of snowfall

74. Which of the following is true of Peking Man?

A. He is the oldest human being           B. He used fire to keep warm

C. He wore form-fitting clothes made from fur with simple tools.

D. He might have been shorter and wider than previously thought.

75. The following are all the possibilities EXCEPT _______ that the Peking Man survived the cold weather.

A. putting up tents to keep the cold out      B. wearing animal fur

C. using fire in their cave                 D. developing gradually to handle the cold.

After moving to the United States, immigrant groups trying to fit in tend to choose high calorie fatty foods in an attempt to appear more American，a new study finds．That's one reason why immigrants approach US levels of obesity within 15 years of moving to America．

The researchers also did an experiment that measured whether or not the threat of appearing un-American influenced respondents' food choices．After being questioned about their ability to speak English，75 percent of Asian-Americans identified a typical American food as their favorite. Only 25 percent of Asian-Americans who had not been asked if they spoke English did the same.

When their American identity was called into question during a follow-up study, Asian-American participants also tended to choose typical American dishes，such as hamburgers and cheese sandwiches．In that experiment, 55 Asian-Americans were asked to choose a meal from a local Asian or American restaurant. Some participants were told that only Americans could participate in the study. Those who chose the more typical American fare ended up consuming an extra 182 calories，including 12 grams of fat and 7 grams of saturated fat（饱和脂肪）.

"People who feel like they need to prove they belong to a culture will change their habits in an attempt to fit in，"said Sauna Cheryan，an author of the study and assistant professor of psychology at the University of Washington." If immigrants and their children choose unhealthy American foods over healthier traditional foods across their lives，this process of fitting in could lead to poorer health." Cheryan added．

Social pressures，the study concluded, are at the heart of the problem．"In American society today, being American is associated with being white．Americans，who don't fit this image even if they were born here and speak English，feel that pressure to prove that they're American," said Cheryan．

小题1:The author wants to show that __________.

A．more and more Asians enjoy high-calorie snacks

B．immigrants tend to eat American junk food to fit in

C．most Americans are at the risk of heart disease

D．all the American people have a bad eating habit小题2:According to the survey, __________.

A．Asian-Americans care less about their health

B．25 percent of Americans like junk food

C．choosing food is related to Asian-Americans' situation

D．immigrants are forced to eat junk food小题3:The underlined word "fare" in Paragraph 4 most probably means" __________".

A．food offered as a meal

B．a person taking a taxi

C．money spent on food

D．an arranged thing to do小题4:According to Sauna Cheryan, __________.

A．what immigrants have done is ridiculous

B．American traditional foods are healthier

C．immigrants risk their health in order to fit in

D．American culture affects immigrants deeply小题5:Which of the following should take the blame for the bad eating habit?

A．The situation of employment.

B．The traditional culture.

C．The American government.

D．The pressures from society.

原发性痛经的主要机理是（）

A.促性腺激素升高

B.前列腺素升高

C.雄激素升高

D.孕激素升高

E.雌激素升高

简述思想作风建设的内容和特征。