Severe Imperfections in the Labor Market Lead to Persistent Wage

Multiple Choice

Severe imperfections in the labor market lead to persistent wage differentials among countries. Some explanations include

A) because workers are not allowed to freely move across national boundaries to seek higher wages.
B) because workers may choose to not move across national boundaries to seek higher wages due to the cultural differences.
C) but these differences are offset by low productivity in low labor cost countries.
D) both a and b