冷冻完成后之食品冻藏时，必须保持食品中心温度于（）
A.-5
B.-18℃
C.-50℃
D.-100℃以下
参考答案：B
用所给单词的正确形式填空。
1. What are you ____________ (do)?
2. Lily is ____________ (swim) now.
3. Lily often ____________ (get) up early.
4. I like ____________ (pear).
5. I go to school ____________ foot.
6. My parents ____________ (be) teachers.
7. Mike is ____________ (read) a book.
8. My birthday is May ____________ (3).
矿井通风的主要任务是什么？
