When mentioning theCaliforniaDepartment of Health Service's efforts in placing antismoking commercials on television, including popular MTV programs, the writer hinted that ______.
A．the proportion of adolescent tobacco users has dramatically decreased
B．many adolescent smokers are successfully persuaded in giving up smoking
C．some teenagers develop the habit of smoking rather than taking weed because cigarettes are relatively cheaper
D. teenager smokers are quite certain about the effectiveness of the antismoking campaign