What Is the "Hydra Effect

What is the "hydra effect"?

A) The renting out of commercial privileges and protections to citizens and companies from other countries.
B) Another way of stating: "The bloody hands and the invisible hand often worked in concert."
C) Stopping drugs in one area causes drug production to increase somewhere else.
D) How the "rest and relation needs" of U.S. soldiers during the Vietnam War were a major stimulus to sex tourism in Thailand.