Horace mann campaigned for all of the following educational reforms except: a. higher teacher salary b. a longer school year for students c. better teacher training d. the widespread use of mcgruffey's readers as a school textbook

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