The berlin wall was built in order to
a. stop the flow supplies from west germany to west berlin
b. prevent food from entering poland
c. prevent the smuggling of arms to anti-soviet-forces
d. prevent east germans from defecting the west germany

The answer is D., as it's known in the history that the Berlin Wall was created so people from East Germany could not escape to the West.

The transcontinental railroad provided a means of fast transportation. it cut a 6 month trip into 6 days, created jobs for many people and encouraged immigration. the homestead act played a huge role in western expansion; it allowed settlers to begin a fresh start, and gave them land in exchange for their residence for up to five years and a small fee.

C. the delegated powers