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【简答题】
Hundreds of years ago, life was 1 harder than it is today. 2 People didn't have any modern machines, and there was no modern medicine, With the development of social economy, the 3 conditions of mankind are becoming better and better. 4 , life today has brought new problems. One of the biggest problems is 5 .Water pollution has made our rivers and lakes 6 ; it skills a lot of fish and pollutes our drinking water. Noise pollution makes us talk louder and become angry easily. Air pollution is the most serious,. and it's bad 7 all living things in the world. Cars, planes and factories all pollute our air every day. Sometimes the polluted air is 8 thick that it like a quilt, which is called smog. Many countries are making rules to fight against pollution; factories must now clean their waste water 9 it is thrown away so that it will be less polluted. Of course, rules are not enough; every person must 10 to fight against pollution.
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【简答题】袋子里有18个大小相同的彩色球，其中红球有3个，黄球有5个，绿球有10个。现在一次从袋中取出若干个球，至少有5个球是同色的。那么，从袋中一次至少取出多少个球？
【简答题】在 25 °C 时,一电导池以 0.01 mol·dm -3 KCl 和 0.1 mol·dm -3 NH 3 ·H 2 O 溶液,测出的电阻分别为 525 Ω 和 2030 Ω ,试求算此时 NH 3 ·H 2 O 的电离度。
【单选题】25°C 时,浓度为 0.1 mol·dm -3 KCl 溶液中, K + 离子迁移数为 t (K + ) , Cl - 离子迁移数为 t (Cl - ) ,这时 t (K + )+ t (Cl - )=1 ,若在此溶液中加入等体积的 0.1 mol·dm -3 NaCl ,则 t (K + )+ t (Cl - ) 应为多少?
A.
小于1
B.
大于1
C.
等于1
D.
等于1/2
【简答题】妈妈拿来两根一样长的木条,每根木条长14厘米,妈妈用绳子将两根木条固定在一起,接头处用去10毫米。捆扎后的木条长多少厘米?
【单选题】一个袋子中有5个大小相同的球，其中3个白球与2个黑球，现从袋中任意取出一个球，取出后不放回，然后再从袋中任意取出一个球，则第一次为白球、第二次为黑球的概率为( )
A.
B.
C.
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