随着能源结构的改善，不同燃料的燃气热水器已走进千家万户．

①燃气热水器若使用时所在空间不通风，会产生一种极易与血红蛋白结合的有毒气体，该气体的化学式是____ 　；

②下表是燃烧1kg不同燃料所产生两种气体的质量．结合数据分析，等质量燃料燃烧，产生导致温室效应的气体最多的燃料是　____ （填编号），产生导致酸雨的气体最多的燃料是____ （填编号），例举一种不产生以上两种环境问题的能源：____ ．

③天然气最主要的成分是甲烷，甲烷在一定条件下和水反应可以制得水煤气（混合气体），反应前后分子种类变化的微观示意图如下所示：

上述四种物质中，A代表的是____ 　（填化学式），可用作燃料的是____ ；

在该反应中，生成C和D的物质的量之比为____ ．

   The early history of the city of Rome involves Romulus and Remus，two orphan boys who，legend says，were raised by a she-wolf．The boys'mother had been murdered by an evil king and the two babies tossed into the river Tiber．When the wolf found them they had washed up on the shore．She perhaps took pity on the crying of the babies and，gently picking them up in her teeth，she carried them back to her cave and fed them on her milk．The boys grew bigger and stronger and，eventually，were found by a herdsman who took them home．He and his wife raised the boys like their own children．When they reached manhood they sought revenge on the king who had killed their mother and driven them from their home．
   They decided to build a city．Unfortunately，they argued over the appropriate site and Romulus killed his brother Remus．Romulus ruled this city — called Roma — for thirty-seven years．
   The city of Rome is one of the most popular tourist attractions in the world．If you travel there you can see a statue of the two baby boys feeding from their mother - the wolf．

They        a month building the new house.

星期天，小刘骑电动自行车以18km/h的速度在长江大堤上匀速行驶了7000m，电动自行车牵引力的功率为150W．求：
（1）小刘在长江大堤上行驶的时间；
（2）电动自行车在这段时间内牵引力所做的功；
（3）电动自行车的牵引力．