What are the three required written materials for all entries

Why was the taiping rebellion significant

What happened 10 million years ago? if u answer, u get 50 ! plz answer ; -;

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