Suppose emigrants are highly educated and received greatly subsidized education in the home country. if that country decided to levy a "brain drain" tax on them, this could
a. encourage education investments.
b. cause immigration.
c. discourage education investments.
d. raise significant revenue for the government.

c. discourage educational investments          

Explanation:

           Brain drain is the concept given to people living one country and goes to another country to work and earn livelihood. It is most commonly termed for those people who are highly educated and migrate to a wealthier foreign country to work and increase return on the human capital investment.

           In the context, if the government of the home country impose a tax on brain drain on people leaving the home country, people would likely to invest less on their education and it would also decrease the number of people from getting a higher education degree in the home country.

Thus option (c) is the correct option.

it should be d or b but i'm sure it's d