Question: State the name of the pair of word that have id of 20 and 50?
SQL: SELECT T1.word, T3.word FROM words AS T1 INNER JOIN biwords AS T2 ON T1.wid = T2.w1st INNER JOIN words AS T3 ON T3.wid = T2.w2nd WHERE T2.w1st = 20 AND T2.w2nd = 50