The 1988 case of Hazelwood v. Kuhlmeier differentiated between student newspapers sponsored by schools and those created solely by students, in stating that which of the selections below are true about those sponsored by schools themselves?

One drawback of voluntary trade is that it a. requires two groups to use a common language b. can make one group dependent upon another for necessary goods c. doesn't occur unless there is a shortage of goods for at least one group d. forces groups to rely on themselves to produce all the goods they need