下列实验操作中,错误的是 A.制取蒸馏水时,为防止烧瓶内产生暴沸现象,应事先向烧

题型:选择题

问题:

下列实验操作中,错误的是

A.制取蒸馏水时,为防止烧瓶内产生暴沸现象,应事先向烧瓶中加入几片碎瓷片

B.测定未知NaOH溶液浓度时,酸式滴定管需用标准酸液润洗2—3次

C.配制0.1mol/L的H2SO4溶液时,将量取的浓H2SO4放入容量瓶中加水稀释

D.燃着的酒精灯不慎碰翻失火,应立即用湿布盖灭

考点:设计实验方案及探究实验
题型:选择题
请将下列方框里所列词汇的正确形式填到短文中,每空限一词,不能重复使用。
 depend        important   similar    contribute     mean      
pronunciation   differ      strength   end up        attend
We can see the 1) __________ between American English British English but they are different sometimes. Many students want to know about the 2) __________ between American English and British English.
At first the language in Britain and America was the same. In 1776 America became a (an) 3) __________ country. After that, the language slowly began to change. For a long time the language in America stayed the same, while the language in England changed. For example, 300 years ago the English talked about "fall".
Today, most British people talk about "autumn", but Americans still talk abut "fall". In the same way Americans still use the expression "I guess" 4) __________ "I think", just as the British did 300 years ago.
At the same time, British English and American English started borrowing words from other languages, 5) __________ with different words. For example, the British took "typhoon" from Chinese, while the Americans took "tornado" from Spanish.
In 1828 Noah Webster published the first American dictionary. He wanted to make American English different from British English, so he changed the spelling of many words. That’s why the words "colour", "centre" and "traveller" are spelt "color", "center" and "traveler" in American English. Except for spelling, written English is more or less the same in both British and American English.
They are also different in the spoken language. For example, Americans say dance /dæns/, and in southern England they say /dɑːns/. In America they 6) p__________ not /nɑt/; in southern England they say /nɔt/. However, most of the time people from the two countries do not have any trouble in understanding each other.
题型:选择题

用数控铣床加工如图所示的轮廓ABCDEFGA试按照教材中所学的代码格式编制加工程序。要求:(1)在给定坐标系下用绝对坐标方式编写加工程序;(2)坐标原点为起刀点也为刀具终点;(3)加工路径为A—B—C—D—E—F—G—A;(4)主轴转速300r/min,进给速度100mm/min,不考虑刀具直径。

题型:选择题

下列哪项不属于即时通讯应用()

A、SMS

B、ICQ

C、QQ

D、MSN

题型:选择题

下列有关实验操作错误的是()。

A.用药匙取用粉末状或小颗粒状固体

B.用胶头滴管滴加少量液体

C.给盛有2/3体积液体的试管加热

D.倾倒液体时试剂瓶标签面向手心

题型:选择题

若要改变已作出的不合格品审理结论时,申请改变的单位应写出书面报告,有批准()

A、管理者代表

B、质量安全部部长

C、总经理

D、技术部门领导

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