The correct answer is answer C ("There are no alternatives to the traditional prison system for drug offenders").
Back in the 1980s, less than 25.000 people in the United States were incarcerated for drug offenses. Since then, the number has sky-rocketed: currently sitting at nearly 300.000. This goes to show how ineffective the hardening of policies regarding drug-related arrests and convictions are at trying to stop the crisis. Drug abuse is not going to stop just because more people are going to prison, mass incarceration just generates more problems within the existent prison system.
Implementing alternative sentencing strategies would definitely be more efficient and less costly for the States until the drug problem is solved, which is an entirely different venture that isn't going to be helped by over-populating prisons all over the country.
Hope this was helpful to you!