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

Which examples are relevant sources for students to use in research? check all that apply. a journal entry written by a professor who is considered an expert a report written by an independent government source a presentation by a company that includes paid information a document published by a renowned organization a scientific paper put out by a non-profit organization a blog whose author tries to sell a product or service