氯乙烯中毒时可致（）
A．肢端溶骨症
B．口腔炎
C．烟尘热
D．下颌骨坏死
E．氟骨症
参考答案：A
It wasn’t such a good present my cousin had promised me. [ ]
A. that
B. as
C. which
D. what
乙炔气管为黑色，允许工作压力（）MPa，氧气管为红色，允许工作压力（）MPa。
