6/28,21/98,18/84,9/42,( )
A.25/60
B.12/44
C.12/56
D.25/78
1.6,18,( ),78,126A.40B.41C.42D.44
2..6/28,21/98,18/84,9/42,( )A.12/56 B.12/44 C.25/60 D.25/78
3.:6/28,21/98,18/84,9/42,( )A.25/60B.12/44C.12/56D.25/78
4.6/28,21/98,18/84,9/42,( )A.25/60B.12/44C.12/56D.25/78
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