请根据句意或括号中的中文提示、英文释义,写出句中所缺单词,使句子通顺。
(每小题1分,共5分)
We have a growing (人口) and therefore we need more food.
We all know that life is not always (平坦的).
As soon as I had made the final decision, I felt very (calm and not worried).
How can you (have enough money to buy something) such a large house?
I like black and red, but my favourite is blue.