Why did politicians in east germany build the berlin wall?

a: flow of east germans out of the country and into west germany was hurting the east german economy.

b: to stop the trade of illegal drugs between east and west germany

c: to keep jewish neighborhoods in berlin separate from german neighborhoods.

d: to prevent u. s. soldiers from sending patrols over into east berlin

the answer is d trust me

can someone me with this question:  

1) the end of the conflict between the north and the south didn’t just mark the end of a war; it marked the end of an entire way of life.” which statement best describes what this statement means?  

a) the southerners were no longer free and were controlled by the northern states.

b) the industrial economy in the north was not sustainable.

c) slavery became illegal, which changed completely the south’s labor force and the agricultural economy was destroyed.

d) the states decided to relinquish their independence and return to britain’s rule.