根据短文内容回答下列问题。

    It's December. It'ssnowing and the weather is really cold in the north of China. You can see manychildren playing with snow. Some of them are making snowmen. Some are skatingon the river, because it's so cold that the water in the river freezes（结冰）. It's a white world.How beautiful! But in Australia now, the weather is hot. Many people goswimming in the sea. They are having a good time. Jimand his friends are playing soccer near the sea. The sunny weather is reallycool to them. They want to swim after playing soccer.

    Why are they swimmingin December? That is winter,isn't it? Yes, it is in China. Butit isn't in Australia. Because China and Australia have opposite(相反的、相对的)seasons in a year.