As shown in the figure, there is a right triangle paper with two right sides AC = 6cm and BC = 8cm. Now fold the right side AC along the straight line ad so that it falls on the hypotenuse AB and coincides with AE, then CD is equal to () A. 2cmB. 3cmC. 4cmD. 5cm

∵ AC = 6cm, BC = 8cm, ∵ C = 90 °, ab = 10cm, ∵ AE = 6cm (properties of folding), ∵ be = 4cm, let CD = x, then in RT △ DEB, 42 + x2 = (8-x) 2, ∵ x = 3cm

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