如图，要使平行四边形ABCD成为矩形，需添加的条件是（$\qquad$）A.AB=BC B.AO=BO C.∠1=∠2 D.AC⊥BD---**Chart/Diagram Description:** * **Type:** Geometric figure (Parallelogram). * **Main Elements:** * **Shape:** Parallelogram ABCD. * **Points:** Vertices A, B, C, D. Intersection of diagonals is point O. * **Lines:** Sides AB, BC, CD, DA. Diagonals AC and BD. * **Intersection:** Diagonals AC and BD intersect at point O. * **Angles:** Angle labeled ∠1 is formed by line segment AB and line segment AC (∠BAC). Angle labeled ∠2 is formed by line segment AC and line segment AD (∠CAD). **Textual Information:** There is no text present in the image besides the labels for points and angles. No question stem, options, or other descriptive text are visible.