根据首字母或汉语提示写出单词。

1. Why don’t you tell US what r______ happened?

2. —Would you like some bread or cookies?

    —N______, thanks. I don't have any food before going to bed.

3. I left my g textbook at home yesterday.

4. People should be taken a p______ examination every year.

5. What ______(科目) are you studying at school?

前期牙本质不正确的描述是（）。

A.是未矿化的牙本质

B.位于矿化牙本质内侧

C.活髓牙中总有一层

D.发育完成的牙比正在发育的牙厚

E.是成牙本质细胞分泌的