The highest elevations in the united states are located in
a. the sierra nevada.
b. the great plains.
c. the rocky mountains.
d. the coastal regions.

during the 20th century, the role of the vice president has evolved into more of an executive branch position. now, the vice president is usually seen as an integral part of a president's administration and presides over the senate only on ceremonial occasions or when a tie-breaking vote may be needed.