Investors Are Able to Reduce Risks by Diversifying an Investment

Investors are able to reduce risks by diversifying an investment portfolio internationally, and the risk reduction effects would be greater if not for

A) volatile exchange rates associated with the current floating exchange risk regime.
B) the different kinds of tax regimes in different countries.
C) the inaccessibility of foreign stock exchanges to most investors.
D) the poor quality of many stocks in international start-up firms.