【判断题】【消耗次数：1】
在给炔烃的命名时，取代基（如异丙基）的位置是可以在2位的。
①
正确
②
错误
参考答案：
复制
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相关题目
【单选题】
关于炔烃的下列描述正确的是
①
分子里含有碳碳三键的不饱和链烃叫炔烃
②
炔烃分子里的所有碳原子都在同一直线上
③
炔烃易发生加成反应，也易发生取代反应
④
炔烃不能使溴水褪色，但可以使酸性高锰酸钾溶液褪色
【单选题】
关于炔烃的叙述不正确的是（ ）。
①
分子里含有碳碳三键的脂肪烃叫做炔烃
②
能使高锰酸钾酸性溶液或溴水褪色
③
易发生加成反应和氧化反应
④
分子里所有碳原子都处在一条直线上
随机题目
【单选题】
阅读理解：阅读下列短文，回答文后问题，选择最佳答案Trees mainly serve man in three important ways: They provide him with wood and other products; they provide him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important．In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil allowing the rain to sink in and also bind(固定) the soil, thus preventing it from being washed away easily；but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When the top-soil is gone, nothing remains but worthless desert.Two thousand years ago，a rich and powerful country cut down its trees to build warships, with which to gain itself an empire．It set up the empire, but, without its trees, its soil became poor and grew weak. When the empire fell to pieces, the home country found itself faced by floods and starvation(饥荒)．3. Land becomes desert after all trees are cut down because __________.
①
A. roots of trees break up the soil
②
B. no tree keeps the rain and protects the top-soil
③
C. strong winds bring a lot of sand
④
D. there are too many rainfalls to make it
【单选题】
阅读理解：阅读下列短文，回答文后问题，选择最佳答案Trees mainly serve man in three important ways: They provide him with wood and other products; they provide him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important．In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil allowing the rain to sink in and also bind(固定) the soil, thus preventing it from being washed away easily；but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When the top-soil is gone, nothing remains but worthless desert.Two thousand years ago，a rich and powerful country cut down its trees to build warships, with which to gain itself an empire．It set up the empire, but, without its trees, its soil became poor and grew weak. When the empire fell to pieces, the home country found itself faced by floods and starvation(饥荒)．1. According to the passage, which is the most important service of trees to man?
①
A. They help him make money.
②
B. They give him cool.
③
C. They give him wood and other things.
④
D. They help him to stop droughts and floods.
【单选题】
These papers___yet.
①
have not written
②
have not been written
③
has not written
④
has not been written