在鼻一鼻窦恶性肿瘤中，发病率最高的是（）
A.上颌窦
B.额窦
C.筛窦
D.蝶窦
E.鼻腔
参考答案：A
定向爆破伴有反应：2Al+Fe2O3Al2O3+2Fe，此反应中还原剂是 [ ]
A．Al
B．Fe
C．Fe2O3
D．Al2O3
Now that you have a job, you must exert (努力) yourself in ______ you do at work.[ ]
A. however
B. no matter what
C. no matter how
D. whatever
Al2O3+2Fe，此反应中还原剂是 [ ]