The correct option is D To clear forest vegetation that could hide Vietcong soldiers.
Agent Orange was a powerful herbicide used by U.S. military forces during the Vietnam War to eliminate forest cover and crops for North Vietnamese and Vietnam Cong troops. The U.S. program, codenamed Operation Ranch Hand, sprayed more than 20 million gallons of various herbicides over Vietnam, Cambodia and Laos from 1961 to 1971. Agent Orange, which contained the deadly chemical dioxin, was the most commonly used herbicide. It was later proven to cause serious health issues.