The correct answer is B) The Vietnamese terrain and climate were harsh and difficult.
The other options of the question were A) North Vietnamese soldiers were highly trained and well-equipped. C) U.S. soldiers were poorly equipped and lacked adequate training. D) Most South Vietnamese helped the Viet Cong and North Vietnamese.
Waging war in Vietnam was difficult for U.S. Soldiers in that the Vietnamese terrain and climate were harsh and difficult.
The United States started to participate in the Vietnam conflict in 1955 when President Dwight Eisenhower supported South Vietnam. After the death of President Kennedy, Lyndon B. Johnston decided to bombard Noth Vietnam after the Gulf of Tonkin incident.
But it was until March 1965, that the US sent troops to battle in Vietnam territory. It was a controversial decision. The US soldiers find so difficult to fight in Vietnam due to the harsh and difficult terrain and weather.