1.( 1) rectangle (2) diamond (3) square

2. Proof: In parallelogram ABCD. DC // AB

=

∴∠DCA=∠BAC.

And f are bisectors on AC.

∴AE=CF.

∴△DCF=S=△BAE(SAS)

∴DF=EB in the same way, DE=FB. A quadrilateral is a parallelogram.

3. Prove that ∵ quadrilateral ABCD is a parallelogram. ∴AB//CD。

=

And point EF are the midpoint of ABDC respectively. ∴EB//CF。

=

∴ Quadrilateral EBCF is a parallelogram.

∴EF=BC。

4. Proof: in RT△ABC and Rt△CDA.

∠B=∠D=90。 AB=CD。 AC=CA .

∴Rt△ABC=s= Rt△CDA (HL)

∴AD=BC .∴ quadrilateral ABCD valley parallelogram. ∫∠d = 90。 ∴ quadrilateral ABCD is a rectangle.

You know, group B 8.9.10.11.12, just tell me the answer.