According to the passage, which of the following posed the biggest obstacle to the development of military forts

A．decreasing the amount of alcohol drunk by drivers
B．teaching young students how to drive safely after drinking alcohol
C．punishing people more heavily for driving after drinking alcohol
D．giving special courses to teach doctors about new drugs and treatments for alcoholics

A．alcoholism is not a major social problem
B．there are no more than a million alcoholics
C．the problem of alcoholism costs thousands of millions of dollars every year
D．alcoholism has caused a million automobile accidents a year