Table: senate_elections_1992
Columns: d_41
d_42
d_43
d_44
d_45
d_46
d_47
d_48
d_49
d_50_o

Question: What is the D48 when the D 50 O is d 31?
SQL: SELECT "d_48" FROM senate_elections_1992 WHERE "d_50_o" = 'd 31'