Is the number of people living in a square mile. In the future, economically developed nations may tey to take care of older citizens due to
incone nations
Population control
Population density
Population growth
one reason for the low standard of living

i am pretty sure that answer is population density.

what are the answer choices?

two jet streams that directly affect the formation of weather in the continental part are a polar jet and a subtropical jet. they are responsible for the transportation of weather systems, which directly affect people. the polar front is the boundary between cold air from the north pole and warmer equatorial air. both the polar jet and the subtropical jet blow from the west to the east, and follow the boundary between cold and warm air.

the strongest jet streams are polar jets, while subtropical jets are somewhat weaker.

the right answer is c. the polar jet stream is generaly stronger than the subtropical jet stream.