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。
(1)We have a growing (人口) and therefore we need more food.
(2)We all know that life is not always (平坦的).
(3)As soon as I had made the final decision, I felt very (calm and not worried).
(4)How can you (have enough money to buy something) such a large house?
(5)I like black and red, but my favourite is blue.
