求翻译：长期以来中国在世界经济市场中累积了大量的外汇储备和巨大的贸易顺差，这使得美国、欧盟与日本等国强烈要求人民币升值，在长期的内外压力下，2005年中国人民银行宣布放弃紧盯单一美元的汇率政策，实行了“以市场供求为基础单一的有管理浮动汇率”制度。是什么意思？

A long time in the world market economy, China has accumulated a large amount of foreign exchange reserves and huge trade surplus, which makes the United States, European Union, Japan and other countries strongly to revalue its currency, in the long-term internal and external pressures, the People's