如图，在△ABD和△BAC中，AD＝BC，要使△ABD≌△BAC，则需添加的一个条件是 （填写一个即可）.---**Figure Description:** * **Type:** Geometric figure. * **Main Elements:** * **Points:** Five labeled points: A, B, C, D, O. * **Lines:** Line segments connecting the points: AD, DB, AC, CB, AB. * **Intersection:** Line segment AC and line segment BD intersect at point O. * **Shapes:** The figure depicts two triangles overlapping, sharing a common base segment AB. These triangles are likely △ABD and △ABC. The intersection point O creates smaller triangles: △AOD, △BOC, △AOB, and △COD. * **Labels:** Points A, B, C, D, O are explicitly labeled. The entire figure is labeled "图6". * **Relative Position:** Points A and B appear to be on a common base line. Points D and C are above the line AB. Point O, the intersection of AC and BD, is located above the line AB. **Textual Information:** * **Question Stem:** Not present in the image. * **Options:** Not present in the image. * **Other Relevant Text:** Only the label "图6" is present.