Why must old currency be taken out of circulation when new currency is made?

Which of the following is one example of an ideological conflict that became one of the causes of world war ii?

The collapse of the roman empire most likely to empower the catholic church because

For in this unit, you read about transitions of power and the formation of newly independent nations in africa, asia, the americas, and the middle east. some of these transitions were peaceful, while others caused long-term instability. why do you think some countries were more successful than others with political transitions? what do you think were the biggest challenges facing newly independent countries? would it have been possible for leaders to prevent these problems before they happened? why or why not?