The wave structure of the polar front and associated upper-tropospheric jet stream is caused by a. surface temperature contrasts between oceans and continents.
b. large-scale mountain ranges.
c. transient weather disturbances (mid-latitude low pressure systems).
d. (all of the above)

Which of the following energy sources is not an example of renewable energy? a. a wind turbine farm b. a clean-burning, coal-fired electric plant c. a hydroelectric dam d. a solar panel mounted on a home

Which statement best explains distribution of natural resources? people tend to settle in locations that have the resources they need for survival. some countries have resources that others lack, so trade between countries becomes vital. fossil fuels come from areas that have mountains and other areas that manufacture synthetic gas. areas with natural resources provide a higher standard of living and better quality of life.

Which statement about portugal is not true? a. it granted independence to its last colony in 1975 b. it has avoided conflict with spain c. it was a leader in european world exploration in the 1400s d. its economy is changing from agricultural to industrial b. it has avoided conflict with spain