A key point in the difference between the United States and the European Union as OCAs, is that:

A the intra-European Union trade is significantly higher than the intrastate trade in the United States.

B the intra-European Union trade is significantly lower than the intrastate trade in the United States.

C the intra-European Union labor migration is much higher than the intrastate migration in the United States.

D in the United States the language creates a significant barrier.

Explain your answer thoroughly