Which describes why theories can change or be replaced?

a)theories are based on experiments, and new methods and technologies can yield new results that require the theory to be revised.
b)theories are facts, and new methods and technologies can yield new facts that require the theory to be revised.
c)theories are based on a single hypothesis that can change with each new experiment.
d)theories are single facts that change with each new experiment.

Which of the following was a factor that attracted settlers from the east to the oregon country in the 1840s? a. the absence of native americans in the oregon country attracted many eastern settlers to the region. b. the discovery of gold in 1848 caused a huge migration of people into the oregon country. c. the oregon country’s status as an area of religious freedom attracted many mormons from the east. d. married couples could claim 640 acres of free land in the oregon countr