决定牙轮钻头工作寿命最关键的因素是（）。A、牙齿 B、巴掌 C、牙齿和轴承 D、牙轮

在△ABC中，若（sinA+cosA）（sinB+cosB）=2则△ABC的形状为（　　）

A．直角三角形

B．锐角三角形

C．等腰直角三角形

D．钝角三角形

不等式a²+8b²≥λb（a+b）对于任意的a，b∈R恒成立，则实数λ的取值范围为

任务型阅读（阅读短文并回答问题）

Robot Green was 31years old when he went to college. That was his first time he came into the classroom. Eleven years later he received a doctor’s degree in physics. Robert Green was a good example in studies for all people. His life was a moving story.

From a young age, Robert Green lived a simple and poor life with his grandfather in the mountains of Boston. His grandfather taught him to read. Later he taught himself to read Maths books and Physics books. From time to time, he bought old books with his saved money and read them all. At that time few people in Robert’s neighbourhood knew about his love of reading and learning. But one person, Jane Keller did know him. She worked in a library. Robert used to go there and he read everything in it. She suggested books for him to read.

A year later, he entered Bethel College. He was interested in everything that he had never seen before. He got an A in every subject. To his teachers’ surprise, he finished college in three years. His teachers encouraged him greatly and he went on his education at Stanford University.

小题1:What did Robert buy with his saved money at his young age?

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小题2:Where did Jane Keller work?

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小题3:How did Robert get on with his every subject in Bethel College?

___________________________________________________

小题4:Why were Robert’s teachers surprised at him?

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小题5:What do you think of Robert Green?

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材料一 我国南方某水乡，20世纪80年代初为解决家畜饲料问题从南美引进了一种速生水生植物水葫芦，近几年却发现它已经泛滥成灾，由于其干物质含量仅5%左右，有机物含量很少，利用价值极小，已对当地生态造成严重的破坏，而据考查，原产地无此现象。

材料二 有“植物王国”和“基因宝库”美称的云南，由于一些外来物种的入侵正发生生态危机。紫茎泽兰原产美洲，十多年前经东南亚侵入云南。紫茎泽兰的毒素会使牛羊中毒，其种子又多又小，散落范围大，生存能力强，能到处传播，所到之处草木都无法生长，紫茎泽兰生长特别快，正以每年30kg的速度向北蔓延，一直扩展到四川西南部的凉山地区。根据上述材料回答下列问题：

(1)水葫芦、紫茎泽兰生长失控的原因主要有营养丰富、气候适宜、无天敌等理想条件，它们的生长呈现出___________型的生长曲线。

(2)如果不采取有效措施制止这场生态灾难，其严重后果有___________。它们在原产地却没有出现此严重后果，原因是_________。

(3)水葫芦失控对水体的危害是使水体遭到严重污染，溶解氧大量减少，水生生物大量死亡，水质恶化变臭等。这种危害类似于水体的____________。

(4)为达到既控制水葫芦的“疯长”，又防止使用药物污染环境的目的，有人设想引入水葫芦的天敌。你对此设想有何建议？_____________。

(5)再读材料二，请你提出一项有价值的研究课题。_______________。

在工业生产过程中，事故预警信息的（）关系到整个预警的成败。

A．准确性

B．连贯性

C．完备性

D．快速性