The "Brain Drain" Phenomenon Refers To

The "brain drain" phenomenon refers to:

A) A disease in which the victim's brain shrinks.
B) Workers experiencing a fall in productivity levels due to a lack of up-to-date training.
C) The underemployment of highly skilled immigrants in occupations that do not make a good use of their skills.
D) The event of less-developed countries losing their best and brightest workers through immigration to more developed ones.
E) The event of highly skilled, white-collar workers withdrawing from the labour force.