A、Because cannabis proved to be more harmful than tobacco. B、Because cannabis is already so widespread. C、Because it is not know

M: Lesley, again and again these days we hear tile words "he’s on drug" and many people feel that these illegal drugs are harmful and people should be prevented from getting hold of them in any way at all, because of the damage they can do. What do you feel about this?
W: Oh, yes, you.., you’ve got to have some sort of control, because it has been proved that these some sort of thing, (19) can do irreparable damage, and I know a horrible story about a 16-year-old kid who is in mental hospital now. She went to a party and she took something there and now (20) she’s convinced she’s an orange and she won’t go out of the room for fear somebody’s going to squash her.
M: Lesley, how wide spread is the use of so-called illegal drugs in England?
W: Well, as regards cannabis (大麻)…um… (21)I think as yet little is known about it. I think it may be a rash thing to legalize it now when so little is known, but it must be said that no positive harm has been proved.
M: In view of hostility towards the so-called illegal drugs in things like newspapers and television, why do so many young people take drugs?
W: Well, I think there are many reasons. One of the reasons is because of hostility. (22)It’s the job of the younger generation to reject all the values of the older generation, and it’s just as well for human society that this is so, because otherwise we would never change it or make it better.