Answer:
A. the brain drain
Step-by-step explanation:
Brain drain is a concept that refers to the emigration or movement of majority of the highly skilled and educated individuals from one region to another, which is mostly due to poor working conditions or poor remuneration being offered in areas where they are moving away from, in search of greener pasture.
For example, over the years, there have been a consistent brain drain in the health sector of developing African countries such as Nigeria. Due to the poor working conditions in Nigeria with poor pay package, many top performing medical students, highly skilled doctors and nurses have migrated to countries such as the US and Canada, where good working conditions and remuneration package is obtainable.