根据要求，改写下列句子。
1. I arrived in Beijing before dark yesterday. (改为一般疑问句)
2. Our plane leaves at ten o'clock tonight. (改为否定句)
3. Leo and David are the same age. (保持句意基本不变)
4. He put on his warm clothes because of the cold weather. (对划线部分提问)
5. He will work hard. He will be able to catch up with the others. (用if合并句子)
1. Did you arrive in Beijing before dark yesterday?
2. Our plane doesn't leave at ten o'clock tonight.
3. Leo is as old as David. / Leo and David were born in the same year.
4. Why did he put on his warm clothes?
5. He will be able to catch up with the others if he works hard.