Marijuana Users in the 1960s Were Less Likely to Develop

Multiple Choice

Marijuana users in the 1960s were less likely to develop drug dependence than users starting around the year 2000. This trend MOST likely reflects that:

A) the THC content in marijuana has increased.
B) people started using marijuana at earlier ages.
C) marijuana is now consumed via multiple routes.
D) medical marijuana is legal in a number of states.