Why is agriculture often considered to be an example of perfect competition?

Which of the following answer best explains the ideals or principles led to the concept of manifest destiny? a americans wanted the european countries to stay out of the north american continent. b americans felt they had a god-given duty to protect the land of the native americans. c americans thought they had a god-given duty to spread their culture and government. d americans learned about this concept from the native americans tribes had encountered.