题干

关于“苔痕上阶绿”中植物的描述,正确的是(    )

A:茎中有导管

B:靠种子繁殖

C:叶中有叶脉

D:是监测空气污染程度的指示植物

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D

同类题2

      阅读下文,回答相关问题

                                                                                             飓风:自然的暴力
      ①2004年是否是飓风之年?如果你生活在美国,你的回答无疑是肯定的,因为在1个月内,佛罗里达州已经3次遭遇飓风袭击,造成上百亿美元的经济损失。由于美国人主宰着世界媒体,飓风的消息在全球引起广泛关注。现在,第4个热带风暴珍妮又袭击加勒比海局部地区,它带来的暴雨和洪水在海地造成上千人死亡或失踪,使更多人无家可归。热带风暴和飓风到底是什么系?              ?            ?
      ②飓风是一种热带气候,它是热带海洋上的一个强低气压区,被狂暴的旋转风包围。在北大西洋、在国际日期变更线以西的东北部太平洋以及东经160度以东的南太平洋上,它被称为台风,在印度洋上又被称为旋风。
      ③当热带气旋的风速达到每小时120千米,就正式称为飓风,风速在每小时120千米以下都称为热带风暴。每年,热带地区海洋上产生大约100个热带风暴,其中约50个达到飓风强度。飓风一词源于“Hudcan”,是加勒比海传说中的邪恶之神。
      ④飓风的形成需要精确的气象条件:海平面温度需要高于26.5℃。它们的动力是水蒸气释放的能量:温暖的热带海平面上的空气吸收海水热量后迅速旋转上升,形成一片超低压区域,成为风暴眼。
      ⑤飓风季节从6月1日开始,持续到11月30日结束,最具破坏力的飓风通常出现在8月中旬至10月中旬。
      ⑥首先,在最极端的情况下,飓风可产生最高速度每小时320千米的强风,只有最坚固的建筑才能抵挡如此强的风。其次,它们总是携带暴雨,可能引发灾难性的洪水。第三,最为可怕的是,飓风有时会引发风暴潮现象。所谓风暴潮就是狂风和超低气压携手造成的海平面上升。上升的高度最高可达到7.5米。飓风推动水位提升的海水抵达海岸可能造成洪水滔天。
      ⑦飓风一旦抵达陆地,由于断绝了热海水提供的热能,通常迅速偃旗息鼓。但是,如果在开阔的海洋上,则可持续两个星期,甚至1个月。
      ⑧科学家试图弄清楚海面温度如何影响热带风暴的形成。部分影响是直接的:海面热水相当于飓风的燃料;但是,专家相信飓风的形成并非如此简单。海面温度变化总是伴随着部分大气变化,而大气变化又会影响海洋信风的强弱和降雨量的多少。1999年9月15日,联合国发布了一份研究报告,预测在21世纪,全球气候变暖将导致更频繁、更严重的热带风暴、洪水、龙卷风。气象学家彼得森说:“我们确实知道,飓风的猛烈程度与海水温度直接相关。如果全球气候变暖的趋势持续下去,造成海水温度上升,更多、更强的飓风将接踵而至。”但除了人类的影响,各种自然循环同样影响着热带风暴的形成。比如说,当厄尔尼诺——赤道东太平洋南美沿岸海水温度激烈上升的现象——出现时,高海拔风向受到影响,这时大西洋上产生的热带气旋相对较少。飓风的形成同样与同温层风向、海洋局部区域温度、西非的降雨有关。
      ⑨2005年的风暴有:阿琳、布雷特、辛迪、丹尼斯、艾米丽等。造成严重损失的飓风有卡特里娜飓风、丽塔飓风,二者分别是今年大西洋上的第11次和第17次热带风暴。

同类题4

阅读理解

    On a stormy day last August, Tim heard some shouting. Looking out to the sea carefully, he saw a couple of kids in a rowboat were being pulled out to sea.

    Two 12-year-old boys, Christian and Jack, rowed out a boat to search for a football. Once they'd rowed beyond the calm waters, a beach umbrella tied to the boat caught the wind and pulled the boat into open water. The pair panicked and tried to row back to shore. But they were no match for it and the boat was out of control.

    Tim knew it would soon be swallowed by the waves.

    "Everything went quiet in my head," Tim recalls(回忆). "I was trying to figure out how to swim to the boys in a straight line."

    Tim took off his clothes and jumped into the water. Every 500 yards or so, he raised his head to judge his progress. "At one point, I considered turning back," he says. "I wondered if I was putting my life at risk." After 30 minutes of struggling, he was close enough to yell to the boys, "Take down the umbrella!"

    Christian made much effort to take down the umbrella. Then Tim was able to catch up and climb aboard the boat. He took over rowing, but the waves were almost too strong for him.

    "Let's aim for the pier(码头)," Jack said. Tim turned the boat toward it. Soon afterward, waves crashed over the boat, and it began to sink. "Can you guys swim?" he cried. "A little bit," the boys said.

    Once they were in the water, Tim decided it would be safer and faster for him to pull the boys toward the pier. Christian and Jack were wearing life jackets and floated on their backs. Tim swan toward land as water washed over the boys' faces.

    “Are we almost there?" they asked again and again. "Yes," Tim told them each time.

    After 30minutes, they reached the pier.

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