经科学研究发现，元素原子最外层电子数是8或第一层为最外层且电子数为2的原子是很稳定的，而最外电子层电子数是1的元素容易失去这个电子，最外层电子数是7的原子容易得到电子，如果原子最外层电子数是4，其单质在导电方面具有某些特殊的优良性能，如硅原子最外电子层有4个电子，因而常被用作半导体材料。下列可作半导体材料的是[ ]

A．铝Al

B．氧O

C．锗Ge

D．氖Ne

根据句意及首字母提示，补全单词。

1. January comes after D_______.

2. Difficult m_______ hard. They have the same meaning.

3. —How do you c_______ your birthday every year?

    —I often have a birthday party.

4.Kangkang often helps his mother do some c_______ on Sundays.

5. —Did you recite a Chinese p_______ at the party?

    —Yes, I recited one of Li Bai's.