user: Question: Name the reason for change when George W. Greene (D) was the vacator.
Columns: ['District', 'Vacator', 'Reason for change', 'Successor', 'Date successor seated']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Virginia 2nd', 'Vacant', 'Virginia re-admitted into the Union', 'James H. Platt, Jr. (R)', 'January 26, 1870']
SQL:

assistant: SELECT "Reason for change" FROM "Table" WHERE "Vacator" = 'George W. Greene (D)';