Compared with the Eocene, the Oligocene was characterized by

a. the rise of a land bridge connecting North and South America.
b. colder, more variable global temperatures.
c. a change in the Northern Hemisphere from deciduous to tropical forests.
d. warmer, more consistent temperatures.

a. the rise of a land bridge connecting North and South America

Explanation:

Compared with the Eocene, the Oligocene was characterized by  the rise of a land bridge connecting North and South America.

i am a little confused myself with what goes with the letters and what goes with the numbers but ill do my best to you

the cordillera states and grand canyon are along the southwest u.s. and northern mexican pacific.

the great plains and southwest desert are also the prairie and home to many earthquakes too .

the coastal plains have poor soil and many factories started in the south.

is this what u needed? if not i can see what i can do