For many years, scientists couldn't figure out how atoms and molecules on the Earth combined to make living things. Plants, fish, dinosaurs, and people are made of atoms and molecules, but they are put together in a more complicated way than the molecules in the primitive ocean. What's more, living things have energy and can reproduce, while the chemicals on the Earth 4 billion years ago were lifeless.
　　After years of study, scientists figured out that living things, including human bodies, are basically made of amino acids and nucleotide bases. These are molecules with millions of hydrogen, carbon, nitrogen, and oxygen atoms. How could such complicated molecules have been formed in the primitive soup? Scientists were stumped.
　　Then, in 1953, two scientists named Harold Urey and Stanley L. Miller did a very simple experiment to find out what had happened on the Primitive Earth. They set up some tubes and bottles in a closed loop, and put in some of the same gases that were present in the atmosphere 4 billion years ago: water vapor, ammonia, carbon dioxide, methane, and hydrogen.
　　Then they shot an electric spark through the gases to simulate bolts of lightning on the ancient Earth, circulated the gases through some water, sent them back for more sparks, and so on. After seven days, the water that the gases had been bubbling through had turned brown. Some new chemicals were dissolved in it. When Miller and Urey analyzed the liquid, they found that it contained amino acids-the very kind of molecules found in all living things.
61. When did scientists come to realize how the atoms and molecules on the Earth combined to make living thing?
　　A. 4 billion years ago. B.1953.　C. After seven days.D. Many years later.
62. Scientists figured out that human bodies are basically made of .
A.amino acids
B.molecules
C. hydrogen, carbon, nitrogen and oxygen atoms
D. water vapor, ammonia, carbon dioxide, methane and hydrogen
63. Harold Urey and Stanley L.Miller did their experiment in order to .　
A. find out what had happened on the Earth 4 billion years ago
　　 B.simulate bolts of lightning on the ancient Earth
　　 C. dissolve some new chemicals
　　D.analyze a liquid
64. At the end of the last paragraph, the underlined word "it" refers to .
A. a closed loop   B. an electric spark   C.water   D. the liquid
65. According to the writer, living things on the Earth include .
　A. atoms and molecules                     B.chemicals　
C. plants, fish, dinosaurs and human beings     D.the primitive soup

   For many years, scientists couldn't figure out how atoms and molecules on the Earth combined to make living things. Plants, fish, dinosaurs, and people are made of atoms and molecules, but they are put together in a more complicated way than the molecules in the primitive ocean. What's more, living things have energy and can reproduce, while the chemicals on the Earth 4 billion years ago were lifeless.

　　After years of study, scientists figured out that living things, including human bodies, are basically made of amino acids and nucleotide bases. These are molecules with millions of hydrogen, carbon, nitrogen, and oxygen atoms. How could such complicated molecules have been formed in the primitive soup? Scientists were stumped.

　　Then, in 1953, two scientists named Harold Urey and Stanley L. Miller did a very simple experiment to find out what had happened on the Primitive Earth. They set up some tubes and bottles in a closed loop, and put in some of the same gases that were present in the atmosphere 4 billion years ago: water vapor, ammonia, carbon dioxide, methane, and hydrogen.

　　Then they shot an electric spark through the gases to simulate bolts of lightning on the ancient Earth, circulated the gases through some water, sent them back for more sparks, and so on. After seven days, the water that the gases had been bubbling through had turned brown. Some new chemicals were dissolved in it. When Miller and Urey analyzed the liquid, they found that it contained amino acids-the very kind of molecules found in all living things.

1.When did scientists come to realize how the atoms and molecules on the Earth combined to make living thing?

　　A. 4 billion years ago. B.1953.　C. After seven days.D. Many years later.

2.Scientists figured out that human bodies are basically made of .

　　A.amino acids

B.molecules

C. hydrogen, carbon, nitrogen and oxygen atoms

D. water vapor, ammonia, carbon dioxide, methane and hydrogen

3.Harold Urey and Stanley L.Miller did their experiment in order to .　

A. find out what had happened on the Earth 4 billion years ago

　　 B.simulate bolts of lightning on the ancient Earth

　　 C. dissolve some new chemicals

　　 D.analyze a liquid

4.At the end of the last paragraph, the underlined word "it" refers to .

　　    A. a closed loop   B. an electric spark   C.water   D. the liquid

5.According to the writer, living things on the Earth include .

　　    A. atoms and molecules                     B.chemicals　

C. plants, fish, dinosaurs and human beings     D.the primitive soup

完形填空

　　Six-year-old Lena Fugatt liked to sit beside her grandfather while he drove his 3 000-pound tractor around the family farm. One afternoon Ray Fugatt, 58, took Lena with him when he went to 1 a pile of brush.

　　He 2 gasoline on the pile and set fire to it. The brush 3 into flames that engulfed（吞没）him 4 Screaming, Fugatt fell to the ground and 5 to put out the fire. Pushing himself to his 6 , he struggled to where Lena was on the tractor, 30 feet away.“Go to get Lena,”he whispered, using Lena’s name 7 her grandmother. Then he fell down unconscious onto the flat ground.

　　The 8 on Fugatt’s arms had come off, his chest was a 9 of deep red blisters（泡）, and his face was badly burnt. But Lena didn’t 10 Afraid to leave her grandfather alone while she ran for 11 , she realized her only 12 was to drive the huge tractor to the house, a half mile away. Her grandfather had 13 her to drive it alone, but now the 3.5-foot-tall girl decided to do just that.

　　She slid forward on the seat and used her toe to 14 the red started button. The machine moved ahead, and Lena struggled to drive it back to the 15 When the people of emergency（紧急）services arrived, there were huge 16 tracks in the field, showing the girl’s 17 around trees, bushes and ditches（阴沟）.

　　Ray Fugatt 18 second-and-third-degree burns over 40 percent of his body but made almost complete recovery. According to the doctor, he would not have been saved if Lena had not 19 so quickly.“Lena 20 her cool, knew what had to be done, and did it.”

 For many years, scientists couldn't figure out how atoms and molecules on the Earth combined to make living things. Plants, fish, dinosaurs, and people are made of atoms and molecules, but they are put together in a more complicated way than the molecules in the primitive ocean. What's more, living things have energy and can reproduce, while the chemicals on the Earth 4 billion years ago were lifeless.

　　After years of study, scientists figured out that living things, including human bodies, are basically made of amino acids and nucleotide bases. These are molecules with millions of hydrogen, carbon, nitrogen, and oxygen atoms. How could such complicated molecules have been formed in the primitive soup? Scientists were stumped.

　　Then, in 1953, two scientists named Harold Urey and Stanley L. Miller did a very simple experiment to find out what had happened on the Primitive Earth. They set up some tubes and bottles in a closed loop, and put in some of the same gases that were present in the atmosphere 4 billion years ago: water vapor, ammonia, carbon dioxide, methane, and hydrogen.

　　Then they shot an electric spark through the gases to simulate bolts of lightning on the ancient Earth, circulated the gases through some water, sent them back for more sparks, and so on. After seven days, the water that the gases had been bubbling through had turned brown. Some new chemicals were dissolved in it. When Miller and Urey analyzed the liquid, they found that it contained amino acids-the very kind of molecules found in all living things.

61. When did scientists come to realize how the atoms and molecules on the Earth combined to make living thing?

　　A. 4 billion years ago. B.1953.　C. After seven days.D. Many years later.

62. Scientists figured out that human bodies are basically made of .

A.amino acids

B.molecules

C. hydrogen, carbon, nitrogen and oxygen atoms

D. water vapor, ammonia, carbon dioxide, methane and hydrogen

63. Harold Urey and Stanley L.Miller did their experiment in order to .　

A. find out what had happened on the Earth 4 billion years ago

　　 B.simulate bolts of lightning on the ancient Earth

　　 C. dissolve some new chemicals

　　 D.analyze a liquid

64. At the end of the last paragraph, the underlined word "it" refers to .

  A. a closed loop   B. an electric spark   C.water   D. the liquid

65. According to the writer, living things on the Earth include .

　 A. atoms and molecules                     B.chemicals　

C. plants, fish, dinosaurs and human beings     D.the primitive soup