Who was the first man to invent aeroplane

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

Once the constitution was approved, what more had to happen before it could go into effect?

What was the name of the radio talks roosevelt would give to the public called