题目

Valencia is in the east part of Spain(西班牙). It has a port on the sea, two miles away on the coast. It is the capital of a province that is also named Valencia. The city is a market centre for what is produced by the land around the city. Most of the city's money is made from farming. It is also a busy business city, with ships, railways, clothes and machine factories. Valencia has an old part with white buildings, colored roofs, and narrow streets. The modern part has long, wide streets and new buildings. Valencia is well known for its parks and gardens. It has many old churches 科学家提出了一种最经济最理想的获得氢能源的循环体系（如下图）。下列说法错误的是 [     ]A．分解的水的质量等于生成的氧气和氢气的质量和B．氢气和氧气的反应吸收热量C．氢气和氧气的反应属于化合反应D．催化剂在反应前后质量和化学性质不变