Why did the United States become involved in the conflict between North and South Vietnam?

Jack owns a small home near a school. he doesn't have any children, and doesn't plan on having any in the future. jack is a writer and works out of his home. all of the noise from the playground during the day interrupts jack while he is trying to work. tina, a friend of jack's, also owns a small home. her home is in a quiet, little secluded neighborhood. she has a child that will be entering first grade in the fall and wishes she lived closer to a school. one day, jack asked tina if she would want to exchange homes. is this a possibility? a. yes, a trade of properties (exchange) is possible if the trade involves no financing and the properties are not mortgaged. b. yes, a trade of properties (exchange) is possible if the trade involves no financing. c. no, it is not a possibility. simply "trading" real estate is not recognized under california real estate law. d. none of the above