宝石鉴定中常用的紫外光灯平均长、短波长为：（）.
A.245nm和355nm
B.254nm和365nm
C.276nm和395nm
参考答案：B
上颌窦癌向后侵犯，使（）
A.窦外侧骨壁破坏，壁外脂肪密度消失
B.窦部皮下脂肪与肌间隙消失
C.颞下窝结构不清
D.翼突破坏，翼腭窝增宽
E.齿槽骨破坏
It was __________she was injured in the accident _______ she didn’t come to the party yesterday.
A.as; which B. because; that C since; why D. for; how
