A、December. B、February. C、June. D、January. D由原文可知，对于澳大利亚大多数地区而言，1月通常是夏季最热的月份，故答案为D。

Hello, everyone. Today we are going to talk about some general knowledge of Australia. Australia is the world’s smallest continent and largest island. It is one of the oldest land masses and flattest of the continents. After Antarctica, Australia is the second driest continent. Most areas of Australia are semi-desert. Australia is the only nation which occupies an entire continent. It is about 25 times larger than Britain and almost double the combined areas of Pakistan and India. There are three main structural characters: the first one is the Great Western Plateau. It covers most of Western Australia, much of the Northern Territory and South Australia, and part of western Queensland. East of the plateau, extending from the Gulf of Carpentaria in the north to eastern South Australia and the western Victoria coast, is the great lowland belt known as the Central Eastern Lowlands. The last one is the Eastern Highlands, better known as the Great Dividing Range, following the eastern coast south from far northern Queensland to southern Tasmania.
    Nearly a third of Australia is north of the Tropic of Capricorn and the rest is the temperate zone. Low rainfall and clear sky is a feature of the climate on most of the continent. In Australia, summer is from December to February, autumn, March to May, winter, June to August, and spring, September to November. For most parts of the country, January usually is the hottest month in summer.
    Australia has no official or traditional national costume. Green and gold have been used traditionally by Australian Olympic and other sporting teams for most of the 20th century, and have become the national colours formally in 1984. The official language is English—by usage, not law. It has its own colloquialisms and slang but does not differ importantly from other forms of English, except in accent. Spelling generally follows the British form. Australia is one of the most urbanized countries in the world, with about 70％ of the population living in the 10 largest cities and only 15％ of Australians live in rural areas. Australians have a high standard of living by world standards. Australia is a multicultural society with about a quarter of the population foreign-born. The first European settlement of the continent—by the British—began in 1788, on the site now occupied by Sydney. Settlement schemes during the next 150 years helped increase Australia’s population to about 7. 4 million by the end of World War II. Over 5 million migrants have settled in Australia since.
    Questions 19 to 22 are based on the recording you have just heard.
    19. What does the speaker say about Australia?
    20. Which is the hottest month in Australia?
    21. What can we learn about the language in Australia?
    22. What does the speaker say about the population in Australia?