CREATE TABLE table_52240 ("Res." CLOB, "Record" CLOB, "Opponent" CLOB, "Method" CLOB, "Event" CLOB, "Round" FLOAT, "Time" CLOB, "Location" CLOB)

Who was the opponent during the UFC 90 event with a fight that lasted less than 4 rounds?
SELECT "Opponent" FROM table_52240 WHERE "Round" < '4' AND "Event" = 'ufc 90'
SELECT "Opponent" FROM "table_52240" WHERE "Event" = 'ufc 90' AND "Round" < '4'