约分和通分都是改变分子、分母的大小,分数大小不变.______.(判断对错)

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问题:

约分和通分都是改变分子、分母的大小,分数大小不变.______.(判断对错)

考点:约分,通分,最简分数,分数的化简
题型:解答题
脱式计算。
(1)593-138-126(2)504-(216+109)
(3)543-182-197(4)900-429-196
题型:解答题

随机区组方差分析中,总例数为N,处理组数为k,配伍组数b,则处理组组间变异的自由度为()

A.(b-1)(k-1)

B.b-1

C.N-k

D.k-1

E.N-1

题型:解答题

阅读理解

     Nobody has ever succeeded in their attempt to stay young and live a very long life.   1   But is this

really true?

     Dr Aubrey de Grey thinks that we can stop people getting old and that in about 20 years, people

will be able to live to be 1,000 years old!  2  

     In Dr Grey's opinion, getting old is a problem that can be solved.  3    If we can cure this disease,

we can stop the aging process.We can also make people have young bodies again.

     Dr Grey believes that science will soon be able to stop the causes of aging so that a person's body

won't get weak and won't suffer from the typical diseases of old age.

     Dr Grey compares the human body to a house.As the house gets older, some things must be

repaired.Broken hearts must be replaced.The same thing can happen with the human body, he thinks.

We can use stem cell technology to grow new, healthy tissue to replace the old, damaged one.We can

also try to remove diseasecausing molecules in our bodies._5_.

      6    However, they admit that Dr Grey's ideas have not yet been proved wrong.Dr Grey is

convinced that his opinions are realistic and that his research is very important.If aging is a disease, he

says, we must try to cure it.

A. At the same time, people's bodies will stay young and healthy.

B. Scientists succeeded in solving the problem of aging long ago.

C. A lot of scientists think his ideas not realistic.

D. When our bodies change as we get older, this is like a disease.

E. New deadly diseases may also be cured, if we can stop the aging process.

F. It seems that everybody must get old and die.

G. In this way, a person could easily live to be 1,000 years old.

题型:解答题

高压喷射灌浆形成凝结体的形状与喷嘴移动方向和持续时间有密切关系,要形成柱状体则采用( )。

A.侧喷
B.定喷
C.摆喷
D.旋喷

题型:解答题

寒潮将至的时候,蜘蛛会:()

A.大量吐丝结网

B.不再吐丝结网

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