What two groups fought for power in the Soviet Union 1927

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

Has a form of government that has __ within its territorial boundaries

Which of the following was a crop not grown in the olmec farming ? potatoes or squash or maiden or beans