题目

Is There Life on Earth?     There was great excitement on the planet of Venus(金星) this week. For the first time Venusian scientists managed to land a satellite on the planet Earth, and it has been sending back signals as well as photographs ever since. The satellite was directed into an area known as Manhattan (named after the great Venusian astronomer Prof. Manhattan, who first discovered it with his telescope 20,000 light years ago). Because of excellent weather conditions and extremely strong signals, Venusian scientists were able to get valuable information as to feasibilit在一密闭容器中,有甲、乙、丙、丁四种物质,在一定的条件下,充分反应,测得反应前后各物质质量如下表:物质甲乙丙丁反应前质量(g)414210反应后质量(g)待测20631关于此反应,下列认识正确的是( )A.该变化的基本反应类型是化合反应B.参加反应的甲、丙的质量比为1:9C.乙、丁的相对分子质量比一定为19:21D.甲反应后的质量为8g
英语 试题推荐