Final answer:
The correct answer is 'a. Oh', which is the 2-letter word in Roy Orbison's hit song title 'Oh Pretty Woman'.
Step-by-step explanation:
The 2-letter word that precedes "Pretty Woman" in the title of a Roy Orbison No. 1 hit is "Oh". Hence, the correct answer to the question is option a. Oh. "Oh Pretty Woman", released in 1964, became one of Orbison's most celebrated songs, reaching No. 1 on the Billboard Hot 100 chart.
Its opening guitar riff, Orbison's powerful vocals, and the catchy chorus have cemented the song as a classic in music history. It is notable for its influence on rock and pop music and remains popular across multiple generations.