In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Q: Question: What states had soldiers in the Corps that Pierson led the the 1st New York in? Passage:In 1857, he enlisted as a private in Company K of the 7th Regiment of the New York National Guard, and was attached to the staff of Brig. Gen. William Hall. At the start of the American Civil War, Pierson helped organize the 1st New York Volunteer Infantry Regiment, and was appointed captain in May 1861. He was promoted several times and assumed command of the regiment on October 9, 1862, with the rank of colonel. Attached to the 3rd Corps, Army of the Potomac, he led the 1st New York in actions at the Seven Days Battles, Second Manassas and the Battle of Fredericksburg. After the Battle of Chancellorsville in May 1863, Colonel Pierson was honorably discharged and mustered out on May 25, 1863. For distinguished service, he was brevetted brigadier general of the United States Volunteers for "gallant and meritorious services."
Links: a. New York Army National Guard b. Colonel (United States) c. 1st New York Volunteer Infantry Regiment d. III Corps (Union Army)
A:
d