The United States feared that if communism was successful on Vietnam, the rest of the countries that border it would soon turn into communism and those other countries that border that new communist country would also be converted to communism and so on. This is called the "domino theory" and made the United States to send troops to prevent the theory from happening.
The answer would be A transporation cost grew more expensive hope that helped b c or d dont sound right
Favoring or enforcing strict obedience to authority
