根据短文内容，回答下列问题。

    It's December. It's snowy and the weather is really cold in the north of China. You can see many children playing with snow（雪）. Some of them are making snowmen. Some are skating on 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（天气）is hot. Many people go swimming in the sea. (大海) They are having a good time. Jim and his friends are playing soccer near the sea. The sunny weather is really cool to them. They want to swim after playing soccer.

    Why are they swimming in December? It is winter, isn't it? Yes, it is in China. But it isn't in Australia. That's because we, Chinese and Australians, have different seasons(季节) in a year.

下列关于功和机械能的说法，正确的是（   ）

长歌行

《汉乐府》

青青园中葵，朝露待日晞。阳春布德泽，万物生光辉。常恐秋节至，焜黄华叶衰。百川东到海，何时复西归？少壮不努力，老大徒伤悲。