穿刺针、腹腔镜、活检钳在使用前应如何处理（）。
A、福尔马林熏蒸
B、灭菌处理
C、清洁
D、低水平消毒
参考答案：B
It ______twenty years since I came to the school. [ ]
A. are
B. is
C. was
D. were
矿井维修电工上岗必须携带（）的上岗证。
