2003年10月15日，我国第一艘载人宇宙飞船“神州五号”发射获得圆满成功．发射飞船的火箭使用的燃料是偏二甲肼（C2H8N2），燃烧时发生如下反应：
C2H8N2+2X
2CO2+4H2O+3N2，则X的化学式为______． 点燃 .
由反应的化学方程式C2H8N2+2X
2CO2+4H2O+3N2，生成的2个CO2分子、4个H2O分子和3个N2分子中共含有C、O、H、N四种原子的个数依次为2、8、8、6，而反应前1个C2H8N2分子中所含有C、O、H、N四种原子的个数依次为2、0、8、2，根据化学变化前后原子种类、个数不变的原则，可判断2个X分子中共含有4个N原子和8个O原子，则物质X的化学式为N204； 点燃 .
故答案为：N204．
In this section you will find after each of the passages a number of questions or unfinished statements about the passage, each with 4 (A, B, C and D) choices to answer the question or complete the statement. You must choose the one which you think fits best. Blacken the corresponding letter as required on your Machine-scoring ANSWER SHEET.
| Questions 61-70 are based on the following passage. While some international couriers are showing signs of exhaustion, EMS (Express Mail Service), the generic name for the courier services of post offices, seems to be finding its stride. Known as Datapost in Britain, as Chronopost in France, and as A1-Barid al-Mumtaz in Saudi Arabia, EMS is now second in the international courier business (jointly with TNT Skypack). Last year it delivered 5.6 million items, weighing less than 20 kilograms each, across borders. That and its annual growth rate of around 5 percent have worried DHL, the market leader, enough for it to counter-attack in the Courts. On October 26, a Dutch judge ruled against DHL on all three counts filed against the Dutch post office: that the three-initial name was too close to DHL’s; that the orange lines in the EMS logo were too similar to DHL’s dark red ones; and that the claim to the widest route system in the world was unfounded. DHL has threatened the Swiss post office with similar action, but it may reconsider after the Dutch ruling. EMS has some advantages over the private couriers. One is a dense ready-made network of offices, especially in Europe, the avowed target area of the private couriers. Another advantage is a long tradition of working with customs authorities. In a business where minutes count, it pays to have good friends at customs. That advantage particularly irritates the private couriers because there is no legal way to combat such unquantifiable coziness. The private courier services are also annoyed because in countries like Switzerland and Italy, where the post office is officially a monopoly, they pay it a fee. In Switzerland DHL says it pays more than SFr lm ($ 708,000) "to the competition" each year. In France the couriers have won a battle for exoneration. Although governments are under little pressure to keep prices artificially low, EMS is often cheaper than the private couriers, but not always. A recent test in Britain (on a domestic route) showed Datapost about halfway between the least and the most expensive, but gave it full marks for speed and service. Each national EMS is free to set its rates and follow its own rules on things like bulk discounts. The Universal Postal Union, based in Berne, determines how costs and revenues are split between sending and receiving countries, and standardizes procedures. More than 100 postal administrations have linked into the system—and more are coming, including Russia’s. That makes the feisty EMS particularly happy since its rivals have not been allowed to serve anywhere in Russia. |
Which of the following names is NOT used for EMS
A．Datapost
B．Chronopost
C．A1-Barid al Mumtaz
D．TNT Skypack