CREATE TABLE table_55890 ("Name" CLOB, "Entered office" CLOB, "Left office" CLOB, "Political party" CLOB, "Monarchs served" CLOB, "Birth Place" CLOB)

What date did the prime minister who entered office on 7 December 1916 leave office?
SELECT "Left office" FROM table_55890 WHERE "Entered office" = '7 december 1916'
SELECT "Left office" FROM "table_55890" WHERE "Entered office" = '7 december 1916'