正确答案: A

题目：运载火箭的主要燃料是偏二甲肼（用R表示），其反应的化学方程式为：R + 2N2O4 == 3N2 + 4H2O + 2CO2，则偏二甲肼的化学式是

解析：A

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举一反三的答案和解析：

[单选题]（2）电路改正后闭合开关，发现电流表的指针偏转，电压表指针没有偏转，则该故障的原因是 （填下列故障原因的代号）

小灯泡接线短路

[单选题]下面对文段内容理解有误的一项是（ ）

第⑤段介绍了华表原名和艺术价值。

[单选题]14．

For

解析：14．C【解析】固定词组，且句首大写。

[单选题]下列事例中，为了减小压强的是

载重汽车的车轮很宽 D．滑冰鞋上的冰刀刀口很薄

[单选题]下列句子中加点的成语便用不恰当的一项是( )

喷泉伴着音乐铺牺开来，如珠玉迸放，如风吹梳动，如静水花开，在彩灯映照下浮光掠影。

解析：（浮光掠影：比喻印象不深刻，好像水面的光和掠过的影子一样，一晃就消逝。）

[单选题]（孝文帝）“诏不得以北俗之语言于朝廷，若有违者，免所居官。”对于诏令内容理解准确的是（ ）

在朝廷必须说汉语，违反者免其官职

[单选题]8．—What's your________ subject?—English．

favorite

解析：8.C 【解析】你最喜欢的科目，这个句子可以改写成其同义句“What subject do you like best?”．

[单选题]BTom lived a long way from the town．One day he went into the town to buy something in a shop，and after he bought it，he went into a restaurant and sat down at a table． When he looked round，he saw some old people put glasses on before reading their books，so after lunch he went to a shop to buy glasses，too． He walked along the road，and soon found a shop．The man in the shop made him try on a lot of glasses，but each time Tom said，"No，l can't read with this pair． "The man became more and more puzzled． At last he said，"Excuse me，but can you read at all?"No，l can't!"Tom said，"lf I can read，do you think I will come here to buy glasses?"

in a restaurant

解析：26．c[解析】由第一段第二、三句可知．

[单选题]BThe world is not only hungry，it is also thirsty for water． this may seem strange to you，since nearly 75% of the earth is covered with water． But about 97% of this water is sea water．Man can only drink and use the other 3% fresh water that comes from rivers，lakes，under-ground and other places． And we cannot even use all of that，because some of this fresh water has been made dirty．

The amount of fresh water is really very small．

解析：26．A【解析】由第一段的描述可知，人类只有3%的、 淡水可以利用。