听力原文： Four Colombian police officers are dead and at least five more wounded after leftist rebels ambushed a police patrol in the northwestern part of the country. Police officials say about 100 guerrillas from the Revolutionary Armed Forces of Colombia, or FARC, attacked a vehicle carrying the 22-man police patrol in the department of Risaralda. Military officials say they have sent additional army troops to the area. The FARC rebels are in preliminary peace talks with the government of President Andres Pastrana. The Colombian government has been fighting leftist rebels and right-wing paramilitary forces for nearly 40 years. Four Colombian police officers are dead and at least five more wounded after leftist rebels ambushed a police patrol in the _______ part of the country.