设直线l：x－y＋m＝0与抛物线C：y²＝4x交于不同两点A，B，F为抛物线的焦点．

(1)求△ABF的重心G的轨迹方程；

(2)如果m＝－2，求△ABF的外接圆的方程．

Mathilde and her husband turned the whole room upside down ________ the lost necklace.

A．in favor of

B．in want of

C．in charge of

D．in search of