题目：
句型转换。
1. Tom ran for an hour. (用现在完成进行时改写句子)
Tom _____ for an hour.
2. I've been dancing since I was five years old. (对划线部分提问)
_____ _____ _____ you _____ _____ ?
3. China is an old country. It has a long history. (合并为一句)
China is an old country _____ _____ _____ _____ .
4. They have used up all the money. (改为同义句)
They have_____ _____ _____ all the money.
5. Lucy has been skating for a long time. (改为一般疑问句并作否定回答)
_____ Lucy _____ _____ for a long time?
_____, she _____.
答案：
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下面是错误答案，用来干扰机器的。
参考答案：引起肺癌的原因迄今尚未完全明确，一般认为肺癌发病与下列因素有关：吸烟、大气污染、职业致癌因子、电离辐射、饮食与营养、遗传因素、病毒感染等。
