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1.下列命题中的真命题是( ) (A)关于中心对称的两个图形全等. (B)全等的两个图形是中心对称图形. (C)中心对称图形都是轴对称图形. (D)轴对称图形都是中心对称图形. 2.如图1,在(?)2ABCD中,EF∥AB,GH∥AD,EF与GH交于点O,则该图中的平行四边形的个数共有( ) (A)7个。(B)8个。(C)9个. (D)11个. 3.在四边形ABCD中,O是对角线的交点,能判定这个四边形是正方形的条件是( ) (A)AC=BD,AB(?)CD. (B)AD∥BC,∠A=∠C. (C)AO=BO=CO=DO,AC⊥BD. (D)AO=CO,BO=DO,AB=BC.
1. The true propositions in the following propositions are () (A) Two graphs concerning the symmetry of the center. (B) The two graphs of congruence are center symmetrical graphs. (C) The centrosymmetric graphs are all axisymmetric graphs. (D) The axisymmetric graphs are all center symmetrical graphs. 2. As shown in Fig. 1, in (?)2ABCD, EF∥AB, GH∥AD, EF, and GH intersect at point O, then the parallelograms in this graph are There are a total of () (A) seven. (B) Eight. (C)9. (D)11. 3. In the quadrilateral ABCD, O is the intersection of the diagonal lines. The condition that can determine this quadrangle is () (A)AC=BD,AB(?)CD (B) AD ∥ BC, ∠ A = ∠ C. (C) AO = BO = CO = DO, AC ⊥ BD. (D) AO = CO, BO = DO, AB = BC.