MARIB, Yemen (AP) — One tombstone stands out among the growing number of graves of war dead in the cemetery of the Yemeni city of Marib. It has two “martyrs” listed — a father and his young daughter. Taher Farag and his 2-year-old Liyan were among at least 21 people killed when a rebel missile struck a gas station where he’d lined up to fill his car. It was the deadliest attack in a monthslong offensive by Iran-backed Houthi rebels against Marib, the government’s sole stronghold in the north. Marib is now the main front in Yemen’s nearly 7-year-old war, and civilians continue to pay the cost as fighting drags on with little change.