user: Question: Who is the writer of Children of Earth of "Day Four"?
Columns: ['Children of Earth', 'Run time', 'Writer', 'Director', 'Original airdate', 'Viewers (including HD) in millions']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['"Day One"', '1 hour', 'Russell T Davies', 'Euros Lyn', '6 July 2009', '6.472 (6.601)']
SQL:

assistant: SELECT "Writer" FROM "Table" WHERE "Children of Earth" = '"Day Four"';