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69. The wheel was probably invented by ______.
A. a group of early hunters B. the first men on earth
C. a great prehistoric thinker D. the man who made the first cart
70. This selection says that the first wheel may have been a ______.
A. round piece of stone B. heavy log C. piece of metal D. slice of log

Passage Three
Eating in space is different from eating on earth. The food that astronauts carry with them does not look like the food you eat. Some food is carried in closed bags. It is cooked and frozen before the astronauts get it. All the water is removed from the food. In the spaceship the astronaut puts the water back. He “shoots” hot or cold water into the food bag with a special gun. He eats the food through a small hole in the bag.
Other foods come in bite sizes. The astronaut puts a whole piece in his mouth at once. There an be no crambs. Crambs would float around the spaceship and get in the way. Meat and cake often come in bite-sized pieces. Astronauts can’t drink water from open cups. The water would float in drops in the air. The water is put in the special gun. The astronaut shoots the water into his mouth. Eating in space is not easy. Astronauts must learn to eat this way.
71. Some space foods are carried in _______.
A. water guns B. lunch boxes C. closed bags D. crumbs
72. The story does not say this, but from what we have read, we can tell that ______.
you get much hungrier in space than you do
you can’t have water to drink in a spaceship
astronauts must learn many new and different things
you can’t eat anything in a spaceship
73. Why can’t astronauts drink water from cups?
The water would come from the open cups.
The water would spill all over their food.
Crambs would float in the cups.
The cups would float in the air.
74. The main idea of the whole story is that _______.
there is more food and water in space than on earth
eating and drinking in space is a special problem
astronauts can never eat or drink in a spaceship
there is no food or water in a spaceship
75. Which of the following does the story lead you to believe?
Food for astronauts must be made in a special way.
All meat on earth comes in bite-sized pieces.
Astronauts will only eat cakes made from crambs.
Astronauts have to go hungry in a spaceship.

Passage Four
The energy which the sun radiates goes in every direction, and only a minute part of it falls on the earth. Even so, it represents power of about 5,000,000 horsepower (马力) per square mile per day; the sun gives us as much energy every miunte as mankind utilizes in a year. At present, we use this energy indirectly, and it is our final source of power. Coal represents the chemical action of the sun on green plants thousands of years ago. Water power results from the rain formed by vapor which comes from the evaporation of water under the sunshine. Even windmills operate because of air currents set in motion by the different heating affects of the sun in different places. Some day, through chemistry or some type of solar engine, we shall harness this great source of energy more directly. Already a scientist has worked out an engine, surprisingly efficient, in which the sun’s rays are concentrated through mirrors on a tube of water to create steam.
76. How much energy given off by the sun reaches the earth?
A. 100% but indirectly. B. 5%.
C. 50%. D. only a very tiny amount.
77. The reason why all the solar energy falling on the earth can’t be utilized is that ______.
only a very small part is available