根据句子意思，用括号中所给词的正确形式填空，每空填一词。
You will feel happy if you are         (friend) to others.
Sue lives on the          (ten) floor, but she walks upstairs every day.
The hottest season is summer, and the         (cold) is winter in China.
They don't like to eat out. They often cook meals by          (they) at home.