CREATE TABLE table_204_639 (id DECIMAL, "poll company" TEXT, "source" TEXT, "publication date" TEXT, "psuv" DECIMAL, "opposition" DECIMAL, "undecided" DECIMAL)

what is the number of people in opposition in may 2010 ?
SELECT "opposition" FROM table_204_639 WHERE "publication date" = 'may 2010'
SELECT "opposition" FROM "table_204_639" WHERE "publication date" = 'may 2010'