Which issue presents an obstacle to controlling drugs via source control strategies?

One of the obstacles in controlling drugs in terms of source control strategies are the below:

a. The medication exchange is an imperative source o± ±oreign income and source control undermine third world economies. 
b. The measure of outside developed opiates is vast to the point that regardless of the possibility that 75% of the opium showcase were decimated, the United States would in any case require just 10% of the rest of support its medication exchange. 
c. Regardless of the possibility that the legislature of one country was ready to collaborate in lively medication concealment eForts, different countries would be anxious to take advantage of the medication exchange void

What's the question again?