科学家成功破解了神经元“沉默突触”的沉默之谜。此前发现，在脑内有一类突触只有突触

实验证明，在同温同压下，相同体积的任何气体中含有的分子数相同。据此回答以下问题（以下气体均是指同温同压下）：

（1）将同体积的CO（煤气的主要成分）和C₃H₈（石油液化气的主要成分）混合，所得混合气体中，碳、氢、氧元素的质量比为                ；

（2）石油液化气和煤气燃烧的主要反应为：C₃H₈+5O₂3CO₂+4H₂O；2CO+O₂2CO₂，石油液化气灶和煤气灶不能混用。目前管道煤气的用户迅速增加。根据以上反应分析，一户使用石油液化气的用户，在使用管道煤气后，煤气灶具与石油液化气灶构造上的最大区别是                      ；原因是                     ；

（3）面对石油、煤资源日趋减少的情况，人们正在积极开发新能源。你认为21世纪来源广泛、燃烧放热多、无污染的燃料的最佳制取方法是                             。

阅读理解，判断正误。(正确的标T，错误的标F)

     In the front of many American homes you can see a mat (脚垫).This mat is sometimes called

"welcome mat",because many of the mats have the word "welcome" on them.

     Because Americans don't take off their shoes before going into the house,they need a welcome

mat to clean their shoes.If the children don't clean their shoes on the mat,they may be scolded (被责骂)

by their parents.If you go to an American home,please remember to clean your shoes on the mat,or you

may be told to do so."Different countries,different customs(习俗)."

( )1. There are many "welcome mats" in the front of an American home.  

( )2. Every American home has a welcome mat.                            

( )3. When Americans go into the house,they often take off their shoes.  

( )4. It's better to clean your shoes before you go into an American home.

( )5. There are different customs in different countries.                  

牙髓坏死的临床表现是

A．牙齿颜色正常
B．患牙叩诊剧痛
C．牙冠变粉红色
D．电活力测试无反应
E．牙髓冷热测试正常

计算技术站通过能力与改编能力时，（）列车的编组作业按固定作业计算。

A、摘挂

B、军用

C、行包

D、快运货物

（）族的贝叶经，曾记载了傣族先民是如何将野生稻驯化成为人工稻的过程。

A.布朗

B.傣

C.纳西

D.普米