CREATE TABLE table_31396 ("No. in series" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "Production code" FLOAT, "U.S. viewers  ( million ) " CLOB)

Who wrote the episode that was watched by 2.97 million U.S. viewers?
SELECT "Written by" FROM table_31396 WHERE "U.S. viewers (million)" = '2.97'
SELECT "Written by" FROM "table_31396" WHERE "U.S. viewers (million)" = '2.97'