READ TEXT I AND ANSWER QUESTIONS 11 TO 14:

The right to drive or the right to breathe?

Politicians have taken some steps to cut

deaths from dirty air, but more are needed.

In 1554, a band of wandering Jesuits, after

sweating through southern Brazil’s forested

05 coastal hills, stopped by a river on the high

Piratininga plateau and, delighted at its fresh, cool

air, founded the city of São Paulo. Were they to

return now, for much of the year they would find a

grey-brown smog shrouding a metropolis of 18m

10 people and 6m vehicles. The foul air kills t

housands of people a year and inflicts chronic

illness on countless others.

Mexico city has long been notorious for its

polluted air. Fuel burns less efficiently at high

15 altitudes, and thermal inversions mean that the

surrounding mountains trap a layer of cold air

above the city, preventing the dispersal of fumes.

But the surge in car ownership throughout Latin

America since the 1970s means that São Paulo

20 and other Latin American capitals are no longer

far behind. Though at lower altitudes, both São

Paulo and Santiago suffer from thermal

inversions, too

(http://www.cnn.com/2001/TECH/science/)

Preventing in "preventing the dispersal of fumes" (l.17) can be replaced by: