医疗用品按其污染后造成危险的程度，可分几类
A．1类
B．3类
C．5类
D．2类
E．4类
参考答案：B
165. The headmaster ______ a new teacher ______ the students just now.
A．was introduced; to
B．was introducing; to
C．introduced; to
D．introduced; for
TBA/22拉耳间隙设定为（）。
A、0.5MM
B、0.7MM
C、5MM
