B. Wheeled transportation. Horses don’t need wheels and many civilizations existed prior to the invention of the wheel.
The USS Maddox incident, drew the U.S. more directly into the Vietnam War. Which involved <span>two separate confrontations involving North Vietnam and the United States in the waters of the Gulf of Tonkin.</span>
The strength of the federal government
American settlers, Native Americans, and Mexican Americans faced some conflicts in the Mexico cession. They all faced legal, economic, and social discrimination problems.
In short, conflicts over land and water.
Good luck :)
The answer to your question is A
