根据句意和首字母提示，写出所缺单词。
1. There is n___________ in the fridge. I have to buy some.
2. Before you enter the teacher's office, you must k__________ on the door first.
3. Bill Gates is a very r_________ man in the world. He has billions of dollars.
4. Mr Gao is eighty years old, but he has some m___________ ideas.
5. Can you tell me the m___________ of the word? Sorry, you should look it up in the dictionary.
6. Yang Liwei and Zhan Tianyou are national h_________.
7. Some people are p___________ flowers in the garden.