MADRID (MarketWatch) -- Virtual currency bitcoin surged to a fresh high of above $900 on Tuesday before dropping back to $768, according to prices on Mt. Gox. A U.S. Senate hearing on the "risks, threats and promises" of virtual currencies, in which federal authorities indicated they see value in forms of payment such as bitcoin helped contribute to higher prices on Monday. Also, news of funding for a leading bitcoin exchange in China also helped prices. 中国人跑步入场,被视为此轮比特币火箭行情的重要原因。