邓小平说：“从我们党的历史来看，我们全党成熟的标志是第七次全国代表大会，那是在一九四五年。我们从一九二一年建党，经过了二十四年，才成为一个成熟的党。当然，这是从全党来说。作为中央领导，可以说在一九三五年一月遵义会议……就成熟了，这也用了十三年半的时间。”中共两次走向成熟的关键在于（    ）

根据短文内容简要回答下列问题。

    Do you like drinking coke, coffee, juice or milk? Do you often drink them instead of water? However, of all the things we eat and drink, water is the most important. Not all of us understand this but it is quite true. Human body can go without food for a long time, but two or three days without water usually makes people die.

    Many people do not understand how much water the human body needs to work well. What is true is that many people do not drink enough, especially in hot weather. Most people drink only when they are thirsty but often need more water after they take exercise.

    Does anyone know what is the 65%-75% of human body? It is water. If we do not have enough water, we will feel tired and become ill. So, do you know what the best drink is? It's water.

读北方地区图，回答下列问题。