*4. Which environment is noteasy for the iron wire to rust?
A. There is air, but no water, no acid
B. There is water and acid, but no air.
C. There is no air, wateror acid.
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*5. Whichof the following is not a primary color(原色)?
A. Red.
B. Blue.
C. White.
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*6. A lion can eat one sheep in two hours,a wolf can eat three sheepin eight hours and a hyena(一种凶猛的狗) can eat one sheep in eight hours. If all of the animals were ina cage and were given a sheep, how long would it take them to eat it?