井下一旦发生电气火灾，首先应该（）。
A.切断电源灭火
B.迅速汇报
C.迅速撤离
参考答案：A
慢性支气管炎的预防方面，首先应强调（）
A.戒烟
B.改善环境卫生
C.预防感冒
D.避免受凉
E.加强锻炼
She has studied in this school _______ she was seven years old. [ ]
A. since
B. if
C. until
D. after
