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.

　　62. 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) In 1953.
　　C) After seven days. D) Many years later.
　　63. 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
　　64. 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
　　65. At the end of the last paragraph, the word "it" refers to_____.
　　A) a closed loop B) an electric spark C) water D) the liquid
　　66. 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

62. B。从文中第三段可知："Then, in 1953, two scientists...did a very simple experiment to find out what had happened on the Primitive Earth."这说明从1953年起，人类才开始弄明白地球上的生物是怎样由原子和分子结合而产生的。因此B为正确选项。
63. A。文章第二段第一句："scientists figured out that living things, including human bodies, are basically made of amino acids and nucleotide bases."，科学加指出生物包括人类，都是又由]氨基酸和核苷酸构成的。
64. A。第三段第一句中提到：" Harold. Urey and Stanley L. Miller did a very simple experiment to find out what had happened on the Primitive Earth." ，他们做试验的穆德是多了调查清楚地球原始状态发生了什么事。该段第二句说两人的试验方法，放进了些和40亿年前一样的气体。
65. D。见原文最后一句话："When Miller and Urey analyzed the liquid, they found that it contained..."。"当米勒和尤里对液体进行分析时，他们发现它包含有……"，显然it指的就是从句里的liquid。
66. C。文中第一段第二句提到："Plants, fish, dinosaurs, and people are made of atoms and molecules...”，植物，鱼类，恐龙和人都是由原子和分子组成的。该段最后一句说更重要的是，生物有能量而且能够繁殖，而40亿年期地球上的化学物质则是没有生命的。据此排除B项，C为正确答案。