问题描述：
A B C D
× 9
___________________
D C B A
(1) A = ( )
(2) B = ( )
(3) C = ( )
(4) D = ( )
× 9
___________________
D C B A
(1) A = ( )
(2) B = ( )
(3) C = ( )
(4) D = ( )
问题解答：
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