The United States declared the end of its combat mission in Iraq in August and is to withdraw its remaining troops by the end of 2011.  But the security problems plaguing the nation nearly eight years after the U.S.-led invasion show no sign of ending, calling into question what the U.S. will do.   VOA’s Elizabeth Arrott reports from our Middle East bureau in Cairo, on how military challenges and political options in Iraq may be addressed in the year ahead.