种植农作物要合理密植，原因是（ ）
A．增加植株周围的二氧化碳浓度
B．增加吸收光能的作物叶片的面积
C．降低周围空气中氧气的浓度
D．降低周围的气温以增加有机物合成
合理密植是指在单位面积上，栽种作物或树木时密度要适当，行株距要合理．一般以每亩株数（或穴数）表示．株距、行距要多少才算合理，必须根据自然条件、作物的种类、品种特性、以及耕作施肥和其他栽培技术水平而定．合理密植是增加作物产量的重要措施．通过调节植物单位面积内个体与群体之间的关系，使个体发育健壮，群体生长协调，达到高产的目的．合理密植，有利于充分利用光能，提高光合效率．种植过密，植物叶片相互遮盖，只有上部叶片进行光合作用，种植过稀，部分光能得不到利用，光能利用率低．只有合理密植才是最经济的做法．
故选B．
第II卷（选择题共35分） 第四部分：写作（共两节，满分35分） 第一节：任务型读写（共10小题；每小题1分，满分10分） 阅读下面短文，根据所读内容在文章后表格中的空格里填入一个最恰当的单词。 注意：表格中的每个空格只填一个单词。请将答案写在答题卡相应题号的横线上。 Some people believe that greed and selfishness has become the basis of modern society, and we should return to the old traditions of family and community then we will have a better life. To what extent do you agree or disagree with the above opinion? In this fast-paced world, many values are undergoing major changes. While people traditionally prioritize caring, sharing and generosity in life and work, modern people seem to be more self-absorbed and self-concerned. Modern people act selfishly to survive the harsh competition of life. They say that it is a jungle out there. To survive, you have to fight with whatever means that come handy. Obviously greedy and selfishness go perfectly well with such ideas. In a company, employees do everything they can to get better pay and higher position, even at the cost of colleagues. We are in any way advocating any selfish conduct. It is just that people are pressured to act in a certain way due to outside influences. In spite of common practice, it is hard to conclude that modern society is built on greed and selfishness, both of which are not newly invented vocabulary. In ancient times people also did greedy and selfish things though such behaviors were more condemned then. But we can not ignore the fact that people in the past lived a relatively more isolated life and faced less pressure compared with their modern counterparts. Are we happier to share with others and be generous to them? There is no fixed answer either. Some people take great pleasure helping and giving to others while others feel happy doing the opposite. But I personally think that people should not be too selfish. Caring for others can actually encourage the development of a mutually beneficial relationship. In conclusion, modern people appear to be more self-centered than those in the past due to strong outside pressure. However, we should encourage people to know the importance of being caring and generous and to build a mutually beneficial relationship with others. Are Modern People Becoming More Selfish?
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