关于外毒素的特点，正确的是（）。 A.多由革兰阴性菌产生 B.可制备成类毒素 C.多

下图表示温度对萌发种子呼吸作用强度影响坐标曲线，请分析后回答：

（1）在温度为0～40℃的范围内，呼吸作用强度与温度的关系是________________________。

（2）请你预测，当温度达到100℃时，呼吸作用强度是  ___。

（3）呼吸作用的强度，我们可以通过测得_________的多少来确定。

（4）上述分析说明，在生产实际中贮存蔬菜、水果、粮食要保持___________条件，这样可以避免消耗食品中过多的_____________。

用30根1米长的小棒围成一个长方形，围成的长方形面积最大是______平方米，周长是______．

Millions of young people are creating blogs. Millions of others arc reading them. The word "blog" is a short way of saying Web log.
Many popular (36) now offer free, easy ways to create personal Web pages and fill them with writings and pictures. Many young adults use their blogs to write about daily (37) and events in their lives. They also provide a place for people to write their ideas and (38) and react to the ideas of others.
Blogs offer young people a place to show their writings and other forms of (39) . Blogs can also to helpful to connect young people with larger social groups. But some researchers say the (40) blogs can dangerous when read on the (41) by millions of people all over the world.
People are (42) that students are including information in their blogs that create a threat to their own (43) and safely. (44) . This personal information puts them at risk of being sought out by dangerous people who want to harm them.
(45) One way to avoid these problems is by using programs that permit blogs to be. read by "friends only". (46) .

聚碳酸酯制板

水泥种类很多，按其用途及性能可分为（）。

A.通用水泥、专用水泥、特性水泥

B.硅酸盐水泥、火山灰水泥、矿渣水泥

C.油井水泥、低热水泥、铝酸盐水泥