Why does the author discuss the principle of persistence of vision in paragraph 1?
A. To introduce a discussion of human vision
B. To explain how we remember images
C. To support the idea that film is an illusion
D. To compare two types of special effects
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What did Ed do during vacation?
A. He worked for a radio station.
B. He lived in a dormitory.
C. He took a long trip.
D. He visited the man' s family.
【C16】
A. build up
B. bring up
C. put up
D. set up
How many Catholics in Germany signed a petition last year to relax the Pope's opposition to birth-control?
A. One million.
B. Ten thousand.
C. One thousand.
D. One hundred.
Look at the four squares,A ,B ,C , and D, which indicate where the following sentence could be added to the passage. Where would the sentence best fit?
For example, the hot tea in a vacuum bottle does not interact with the environment outside the bottle.
A closed system is isolated from its surroundings.A The energy supply of a closed system is limited and is progressively used up by the processes operating within the system.B The ability of the system to function decreases as the available energy is exhausted. Without any additional energy supplied from the outside, the system's processes cease altogether and no further change is possible in the system.C A mill wheel supplied with water from a non- refillable container is a closed system. Once the container of water is empty, the wheel no longer turns because there is no water to turn it. In a truly closed system, the water would have to be collected below the mill wheel in a second container to ensure that the system did not supply any energy to the outside.D
A. Square A.
B. Square B.
C. Square C.
D. Square D.