题目

Allow children the space to express their opinions ________ they are different from your own. A. until                 B. even if              C. unless                D. before 答案：B 解析: 略如图，已知四边形ABCD是平行四边形，下列结论中不正确的是（ ）A．当AB=BC时，它是菱形B．当AC⊥BD时，它是菱形C．当∠ABC=90°时，它是矩形D．当AC=BD时，它是正方形