阅读理解。 London Mayor Boris Johnson recently outlined (概述) plans to make London 'the cleanest, greenest city on Earth' by the 2012 Olympics, and called  for commitments from other world cities at a climate change conference. Leaders of the world's 40 largest cities met in Seoul (首尔) two weeks ago for a summit (最高级会 谈)  on combating (与……斗争) global warming,  the third one held since 2005. 'What we should do in Seoul is that we will stop the endless addiction of mankind to the internal combustion engine,' said Johnson. An  urban  (城市的) problem 'The problem of our planet is an urban problem,' Johnson said, calling for 'serious rcsults' in Seoul. He said the British capital wants to use the Olympics 'to drive the greening and the improvement of our city' and that London is committed to reduce carbon emissions by 60 percent by 2025. A substantial program Johnson proclaimed himself a 'passionate cyclist' and said he would push ahead (推动) with cycle superhighways (自行车高速公路)  around London. London's air quality problem, he said, was caused by vehicle emissions from 8,300 antiquated diesel buses, which could be replaced by low-carbon vehicles. There were also 32,000 taxis running on diesel fuel (柴油) , which could be replaced by electric vehicles. Johnson said there would be a substantial program in the next few years to produce 'cleaner, greener' buses for his city.  'The age of the diesel bus has got to be over in London. ' 1. How many times have the summits been held in Seoul since 2005? A. Two B. Three C. Four D. Five 2. According to Johnson, what should people do before the London Olympics? A. Call for 'serious problems'. B. Reduce carbon emissions in London, C. Stop the endless addiction. D. Make London the cleanest city in the world. 3. What caused air quality problems in London? A. factories B. water C. low-carbon cars D. buses and taxis 4. According to the passage, which of the following is NOT true? A. London Mayor Boris Johnson pay more attention to the global warming. B. Diesel buses are also popular in the next few years in London. C. Diesel fuel vehicles will be replaced by electric vehicles. D. London is sure to be a cleaner and greener city than before. 5. What is the best title for the passage'? A. Global warming problems. B. London's air quality problems. C. A substantial program. D. London Eyes 'Greenest' City By 2012.