如右图所示：过A作AE⊥BC,AF⊥CD于F,垂足为E,F,∴∠AEB=∠AFD=90°,∵AD∥CB,AB∥CD,∴四边形ABCD是平行四边形,∵纸条宽度都为1,∴AE=AF=1,在△ABE和△ADF中,∴△ABE≌△ADF（AAS）,∴AB=AD,∴四边形ABCD是菱形．∴B...