Final answer:
Walt Whitman revised and expanded 'Leaves of Grass' multiple times throughout his lifetime, resulting in nine different editions from the original version published in 1855 up to his death in 1892.
Step-by-step explanation:
Walt Whitman is renowned for the continual revision of his seminal poetry collection, Leaves of Grass. Throughout his lifetime, he revised and expanded this work multiple times. Whitman first published Leaves of Grass in 1855 and by the time of his death in 1892 had released the collection over the course of six editions. He expanded the original twelve poems to ultimately include more than 400 poems. The answer to how many times Whitman revised Leaves of Grass during his lifetime is D. 9.