BAGHDAD (AP) — A car bomb exploded Thursday along a bustling commercial street in a mostly Shiite area of north Baghdad, killing at least 20 people in the third major attack in the capital this month. Recent high-profile blasts suggest that Sunni insurgents are trying to mount a comeback as the U.S. prepares to leave Iraqi cities in three months and hand over responsibility for security in the capital to the Iraqis. Shaken survivors voiced fears that the blast heralded a return to violence that swept the Iraqi capital before U.S. and Iraqi forces turned the tide in late 2007.—-Contact The Daily Reveille’s news staff at [email protected]