听力原文： Today about 70 countries use Daylight Savings Time(DST). Daylight Savings Time was first introduced during World War I in Australia. During the world wars, DST was used for the late summers beginning January 1917 and 1942, the full summers beginning September 1942 and 1943. In 1967, Tasmania experienced a drought. The State Government introduced one hour of daylight saving that summer as a way of saving power and water. Tasmanians liked the idea of daylight saving and the Tasmanian Government has declared daylight saving each summer since 1968. Persuaded by the Tasmanian Government, all states except two passed a Law in 1971, for a test use of daylight saving. In 1972, New South Wales, South Australia and Victoria joined Tasmania for regular daylight savings, but Queensland did not do so until 1989. Tasmania, Queensland and South Australia have had irregular plans, often changing their dates due to politics or festivals. For example, in 1992, Tasmania extended daylight savings by an extra month while South Australia began extending daylight savings by two weeks for the Adelaide Festival. Special daylight savings plans were made during the Sydney 2000 Olympic Games. The differences in daylight savings in Australia continue to cause serious problems in transport and many other social activities. It also reduces the number of hours in the working day that are common to all centres in the country. In particular, time differences along the east coast cause major difficulties, especially for the broadcasters of national radio and television. Questions 19 to 22 are based on the passage you have just heard. 19. What was the purpose of Daylight Savings Time introduced in Tasmania? 20. Which state was the last to use DST according to the passage? 21. What can we learn about DST in some Australian states? 22. What do we know about the use of DST from the passage?19．