根据句意和首字母或汉语提示，将单词的正确形式写在相应的横线上。

1. You must stop s____________, nicotine (尼古丁) is bad for your health.

2. The girl s____________ a lot of time collecting stamps last year.

3. We were glad to celebrate our motherland, China's s__________ birthday on October 1st, 2009.

4. I like ____________ (土豆) a lot, and my mother usually cooks it in different ways.

5. Which are __________ (重的), elephants or sheep?

美国人本主义心理学家马斯洛提出了需要层次理论。他认为人具有七种基本需要。在这些需要中，最基本的是______。

A．安全需要
B．归属和爱的需要
C．生理需要
D．自我实现需要