Why are shut-off valves located within 12 inches from the "vehicle ends" of a/c service equipment hoses?

Which statement was true in the past but is not generally true today? a. the training and education costs for some jobs will prohibit some people from entering that career be b. young people tend to go into the same job that their parents and grandparents did see c. people need a basic level of education before they meet requirements to professional schools d. people will probably have more than one job in their active working lives