All the Following Are Reasons for the Lower International Mobility

All the following are reasons for the lower international mobility of people than capital EXCEPT which one?

A) The differences in economic return between countries are lower for people than for capital.
B) It is more expensive to move people than capital.
C) People may have to learn another language and adapt to a different culture.
D) International capital transfers have less cumbersome legal restrictions than international movements of people.