The percentage of teenagers who have tried cannabis is ______.

A．is practiced all over the Britain
B．involves taking the student's blood to test drug use
C．aims at driving drag-taking students out of the school
D．is arranged with the help of computer

A．young drug takers should accept drug treatment
B．the police give people a blood test when they are charged
C．children who sell drugs be given penalties
D．transportation of drags be punished