A bomb exploded outside the U.S. diplomatic mission in the Libyan city of Benghazi overnight, an attack that could be retaliation for the killing, in a U.S. drone strike, of al Qaeda's Libyan second-in-command. An improvised explosive device was dropped from a passing vehicle onto the road outside the mission, in an upmarket area of central Benghazi. It exploded moments after, slightly damaging the building's gate, U.S. and Libyan officials said. Washington had confirmed a few hours before the attack that a U.S.-operated drone had killed Abu Yahya al-Libi, a Libyan-born cleric and senior al Qaeda operative, in Pakistan. The...