SHANGHAI/SINGAPORE - China's central bank unexpectedly cut key policy rates for the second time in three months on Tuesday, in a fresh sign that the authorities are ramping up monetary easing efforts to boost a sputtering economic recovery. The People's Bank of China (PBOC) said it lowered the rate on 401 billion yuan ($55.25 billion) worth of one-year medium-term lending facility (MLF) loans to some financial institutions by 15 basis points to 2.5 percent from 2.65 percent previously. In a Reuters poll of 26 market watchers conducted this week, 20 participants, or 77 percent, predicted that the central bank would leave the MLF rate unchanged. Only six respondents forecast a margin...Keep on reading: China central bank cuts rates for second time in three months to support economy