Why did eastern european countries prevent their citizens from traveling to the west?

a.
they wanted to protect them from western influence.

b.
the travel costs were too high.

c.
they knew that they would bring too many westerners home.

d.
they predicted that another world war would start.

Eastern Bloc emigration and defection was a point of controversy during the Cold War. After World War II, emigration restrictions were imposed by countries in the Eastern Bloc, which consisted of the Soviet Union and its satellite states in Central and Eastern Europe. Legal emigration was in most cases only possible in order to reunite families or to allow members of minority ethnic groups to return to their homelands.

Eastern Bloc governments argued that strict limits to emigration were necessary to prevent a brain drain. The United States and Western European governments argued that they represented a violation of human rights. Despite the restrictions, defections to the West occurred.

After East Germany tightened its zonal occupation border with West Germany, the city sector border between East Berlin and West Berlin became a loophole through which defection could occur. This was closed with the erection of the Berlin Wall in 1961. Thereafter, emigration from the Eastern Bloc was effectively limited to illegal defections, ethnic emigration under bilateral agreements, and a small number of other cases.

d is the answer hope this