Correct Answer: (b) A weed-killing chemical used by the US military in the Vietnam War
Solution:Agent Orange (or herbicide orange) is one of the herbicides and defoliants used by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1962 to 1971. Agent Orange, which contained the chemical dioxin, was the most commonly used and most effective herbicide. It later caused serious health issues such as tumors, birth defects, rashes, and cancer.