题目内容：
Australia is the greatest island in the world. It is to the south of the equator. So when it is summer in our country, it is cold winter in Australia. Australia is big, but the population（人口）there is thin. The population is the same as that of Shanghai, a city of China. Australia is young and diverse nation and Australian people come from many different countries. Australia has many, many sheep. After a short drive from town, you will see sheep around you. You can also find kangaroo has a “bag” below its chest. The mother kangaroo keeps its baby in the “bag”. Australia is considered to be a relaxed, informal society（社会）. When greeting others, students and young people say “Hello” or “Hi”. Sometimes they will say “How’s it going?” or “G day”. In more formal（正式的）situations they usually shake hands the first time they meet. “Good morning”, “Good afternoon” or “Pleased to meet you” are formal greetings. English is Australia’s national language. (请根据上述段落回答第16-20题)1. Australia is the greatest island in the world. The word “island” may mean _______.（单选）—5分A 国家
B 城市
C 山脉
D 岛屿
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