搜题请搜索小程序“爱下问搜题”
问题 选择题

鲫鱼游泳时，前进的动力主要来自（  ）

A．尾鳍的摆动

B．胸鳍和腹鳍的摆动

C．各种鳍的共同作用

D．躯干部和尾鳍的摆动

答案

答案：D

鱼的各种鳍在游泳时主要起维持身体平衡的作用，不要误认为游泳时的主要动力来自各种鳍的摆动。

选择题

伊格洛克中学的一名学生以《我们到底有多蠢》一文赢得大爱达荷瀑布市科学大会的一等奖。他在论文中呼吁人们签署一项请愿书，要求对一种名为“一氧化二氢”的化学物质进行严格控制，或者完全予以废除。因为：①它有可能引发过多出汗和呕吐；②它是酸雨的主要成分；③处在气体状态时，它能引起严重的灼伤；④发生事故时，吸入也有可能致命；⑤它是腐蚀的成因；⑥它会使汽车制动装置效率减低；⑦在不可救治的癌症病人肿瘤中已经发现该物质。以下观点是同学们读后发表的见解，你认为错误的是[ ]

A.不能责备那些无生命、无意志的化学物质，环境问题的主要责任应该是制造这些物质的化学家和生产者

B.环境问题的出现和恶化是人类忽视了与环境保持和谐，解决这些问题不能不依靠化学

C.化学能够既满足人类物质生活不断提高的需要，又防止环境问题的产生和恶化

D.我们经常被搞假科学的奇淡怪论者所吓倒，造成不必要的心理恐慌

查看答案
单项选择题

In the United States in 1986, the average rate of violent crime in states with strict gun-control laws was 645 crimes per 100,000 persons—about 50 percent higher than the average rate in the eleven states where strict gun-control laws have never been passed. Thus one way to reduce violent crime is to repeal strict gun control laws.
Which of the following, if true, would most weaken the argument above

A．The annual rate of violent crime in states with strict guncontrol laws has decreased since the passage of those laws.

B．In states with strict gun-control laws, few individuals are prosecuted for violating such laws.

C．In states without strict gun-control laws, many individuals have had no formal training in the use of firearms.

D．The annual rate of nonviolent crime is lower in states with strict gun-control laws than in states without such laws.

E．(E) Less than half of the individuals who reside in states without strict gun-control laws own a gun.
查看答案