在下列各句的空白处填入一个最恰当的单词，使句子意思完整，语法正确。

1.  You shouldn't cat the food before           it because it's too cold.

2.  There arc a hundred years in a           .

3.  The dish is so delicious that I will never forget its           .

4.  Confucius was one of the greatest thinkers in            China.

5.  My sister doesn't like lemons because they are very           .