据不完全统计，中国青少年网民达1．95亿，有许多青少年正在受到网络低俗、淫秽色情、以及恐怖暴力的伤害，相关案件时有发生。上述材料警示我们（    ）

在“探究实心圆柱体对地面的压强与哪些因素有关”的实验中，某中学一小组的同学们认为此压强跟圆柱体的密度ρ、高度h、圆柱体底面积S是有关的，但有怎样的关系看法不同，于是，在老师的帮助下，小组的同学们从实验室里挑选了由不同密度的合金材料制成、高度和横截面积不同、质量分布均匀的实心圆柱体做实验，测出实心圆柱体竖直放置时（如图所示）对水平桌面上海绵的压下深度，实验记录见下表．

序号	物体	底面积S/cm2	高度h/cm	海绵被压下深度/cm
1	合金甲圆柱体A	10	5	0.5
2	合金甲圆柱体B	10	10	1
3	合金甲圆柱体C	20	10	1
4	合金乙圆柱体A	10	5	1.5
5	合金乙圆柱体B	10	10	3
6	合金乙圆柱体C	20	10	3

  

食物链和食物网中的各种生物之间的关系是（　　）

读中国的四大地理区域图，回答下列问题

阅读理解
    Different weather makes people feel different．It influences health，intelligence and feelings．
    In August，it is very hot and wet in the south the US．People there have heart trouble and other kinds of health problems during this month．In the Northeast and the Middle West，it is very hot in the summer and very cold in the winter．People in these states have more heart trouble after the weather changes in February or March．
    The weather can also influence intelligence ． For example，in a 1983report by scientists，IQ(智商)of a group of students was very high when a very strong wind came, but after the strong wind,
    Their IQ was 10% lower than before. The wind can help people have higher intelligence. However,very hot weather can make it lower. Students in many schools of the US often get worse in exams(考试)in the hot months of the year(July and August).
    Weather also has a strong influence on people's feelings．Winter may be a bad time for thin people．They usually feel cold during these months．They might feel unhappy during cold weather．But fat people may have a hard time in hot summer．At about 18℃people become stronger．Low air pressure may make people forgetful．People leave more bags on buses and in shops on low-pressure days．
    Are you feeling sad，tired，forgetful，or unhappy today？It may be the weather's problem．