C because it is comparing one thing as being "brighter" than the other
The concept of GroupThink was developed by Irving Janis. The term was derived from George Orwell's book "1984" William H. Whyte.
My source was Wikipedia.
The reason for this was because the Irish were trying to escape from political and religious persecution. Also, when the Irish potato famine began people started to migrate then. So basically, persecution, fear, natural disaster, poverty and unemployment.
The economy drastically slow downs as money loses its buying power
That would be called the crude birth rate (CBR). I'm not sure what answer you are looking for, but I hope this helps!