民族矛盾往往是造成一些国家分裂和解体的一个重要原因，然而我国却向世人展示了国家统一、政局稳定、经济发展的景象。民族区域自治是我国一大政治优势，它使各族人民各得其所、和衷共济。下列说法符合我国民族区域自治制度的是（  ）

①自治机关享有变通执行权和立法自治权

②自治地方分为自治区、自治州和自治县(旗)三级

③自治机关是自治地方的人民政府和人民法院

④各少数民族居住的地方都可以实行区域自治

阅读理解

　　Lang Lang is a famous Chinese pianist. He was born in 1982 in Shenyang. He showed his talent(天赋)for playing the piano when he was two. He began to take piano lessons at the age of 3. At the age of 5, he won the Shenyang Piano Competition. When he was 11, he won the first prize at the Fourth International Young Pianists Competition.

    He began his study at Curtis Institute(学院)in America when he was 15. He became the first Chinese student at the institute. During his study there he made great progress and became a top pianist. On August 14th, 1999, the great Andre Watts was ill so Lang Lang played at concert instead of him and he was successful. Then he became famous all over the world.

    In August of 2008, more than 5 billion people watched Lang Lang's performance at the opening ceremony(开幕式)of the Beijing Olympic Games. He also played at the opening ceremony of the Shanghai Expo(世博会).

 烧杯里有360g水，插入两根电极进行电解。当一个电极收集到6g氢气时，另一个电极收集到氧气多少克？