You may have known several kinds of police --- traffic police, fire police and street police. But have you ever heard of energy-saving  policeman? A group of 22 energy-saving policemen went to work last week in Beijing. They go around the city to see the use of energy in hotels, office buildings, shopping centers and other public places. One of their aims is to make sure that these places have set their air conditioning  no cooler than 26degC. They also set up a special phone line so that people can tell them which buildings fail to follow the rule. "If everyone sets their air conditioning at 26degC, Beijing will save 400 million kilowatthour of electricity in one summer. That's one-third of all the usages of the city in the season," said a TV advertisement. Other Chinese cities, like Wuhan in Hubei Province and Yangzhou in Jiansu Province, are going to follow Beijing's steps in setting up a similar police team. As one of the fastest developing countries, China is using a lot of energy. This has a great effect on the country's environment and limited  energy. From 1986 to 2005, the country experienced 20 warm winters continuously . Numbers show that Chinese cities have to spend billions of yuan solving environmental problems every year. At the beginning of this month, China made its first action plan to fight pollution. It aims to reduce energy usage by 20% and increase renewable  energy up to 10% from 7% by 2010. To introduce the public to a green life, last week Beijing held a show on energy-saving technology and productions. Environment-friendly machines, such as a vending machine that helps collect used bottles, have attracted lots of attention. "We want to tell people that there are certain ways to protect the environment. Each of us can find effective ways to do it on our daily lives," said Liu Qianguang, an environmental engineer in Beijing. Which of the following years' winters were all warm in China?
1968--1988. 1999--2003. 2002--2006. 2005--2009.