拔除哪个切牙时最宜用旋转力（）
A.上颌中切牙
B.上颌侧切牙
C.下颌中切牙
D.下颌侧切牙
E.以上切牙均可
参考答案：A
（）是消防员在易燃易爆场所抢险救援时着装的消防防护内衣。
18. I decided to write about Chaplin, one of ______ films I had seen several years before.
A．whose
B．whom
C．that
D．which
