CREATE TABLE table_2891 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "U.S. viewers  ( million ) " CLOB, "Original air date" CLOB, "Production code" FLOAT)

What is the series number of the episode that aired March 25, 2010?
SELECT MIN("No. in series") FROM table_2891 WHERE "Original air date" = 'March 25, 2010'
SELECT MIN("No. in series") FROM "table_2891" WHERE "Original air date" = 'March 25, 2010'