Final answer:
Edwin Arlington Robinson was primarily a poet, and the hypothetical options provided do not reflect factual information about his literary career. He maintained his focus on poetry despite early challenges and eventual success, which included winning three Pulitzer Prizes.
Step-by-step explanation:
Edwin Arlington Robinson is best known for his poetry. However, your question seems to involve a hypothetical scenario rather than factual information about Robinson's work. In actuality, Robinson did not switch from writing one literary form to another because of lack of success or changing times. Instead, he was predominantly a poet throughout his career. Robinson's early struggles were due to the initial unpopularity of his work. Over time, his poetry gained recognition and he became a highly respected literary figure, winning three Pulitzer Prizes for his poetry.
As for why Robinson or any writer might change literary forms, it could stem from various reasons such as their personal interest, reception by readers and critics, or a desire to experiment with new forms. Literature, in its broadest sense, encompasses fiction, non-fiction, poetry, and prose, and includes major forms like novels, short stories, dramas, and essays -- all evolving and influencing writers over time.
Answering the quiz based on historical facts, none of the answers provided—novels, plays, essays, or children's books converting into short stories, poetry, screenplays, or biographies—accurately reflects the transition in Robinson's work, as he was primarily a poet throughout his career.