Choose the correct letter, A, B or C. [br] The number of vehicles on the road __

D: Hi Anne. How’s it going?
A: Oh, Hello Devin. I’m OK, I suppose, but it’s just that I’ve got so much work to do and this morning my tutor set another project and I’ve no idea what to do for this one.
D: What’s it about?
A: Well, we have to choose a topic but it’s got to be related to transport in some way. I honestly have no idea. I was just going to the library to get some ideas.
D: I don’t know if this will be any help but I saw a TV programme last week about traffic problems — it was really interesting — you may be able to still catch it online.
A: What was so interesting?
D: Well, a lot of it was looking at congestion in different countries — I didn’t realize it was so bad. Did you know that there are around 800 million vehicles in the world — I think that’s what they said — and this figure is growing all the time by about 50 million every year apparently.
A: That’s amazing! What’s going to happen to them all?
D: Good question. I think they said the number would double in the next two decades. And of course, all that traffic causes congestion, which costs the economy mil-lions. I think they said that in the US it costs the economy $100 billion every year.
A: Well, they do drive a lot of cars.
D: Yes, but it’s happening all over the world. In Moscow, they lose around $12 billion a year and of course nations like China and India are growing all the time. More cars mean more time wasted sitting in traffic jams.
A: So what’s the solution?
D: Well, there’s been a great deal of research into the whole congestion problem and numerous solutions have been put forward. For instance, in some Chinese cities they restrict road use by banning certain motorists from driving one day a week, depending on their car registration number and you know about the congestion charge in London, where you have to pay to drive in certain parts of the city.
A: So is there anything that can be done about it?
D: Well, one measure that has been introduced is on the M25 motorway, which goes round London. They’ve set up a system whereby experts use real-time data collected from monitors on the motorway and analyse it in order to set speed limits.