What led to the rise of cities in Central and South America? A.
an increase in the surplus of food and a rise in population.
B.
a source of cheap building material.
C.
people needed a place to rest after hunting for animals all day.
D.
farmers planted seeds and cities started to grow.

In a study, people were asked to imagine simple occasions that made them happy and to remember events that made them feel proud about themselves. it was observed that the subjects developed an increasingly positive attitude. these changes are known to be healthy, leading to greater physical activity and reducing unhealthy habits. based on this excerpt, we can conclude that a positive attitude .