在我国,引起原发性肝细胞癌的最重要相关因素是()。
A.丙型肝炎病毒
B.乙型肝炎病毒
C.甲型肝炎病毒
D.黄曲霉毒素
E.酗酒
参考答案:B
水泥中混入六价铬时可增强什么作用
A.致敏
B.致癌
C.中毒
D.致纤维化
E.刺激
Your desk is crowded with too many unnecessary things,including used papers and books.You'd better
________some of them.[ ]
A. remain
B. resist
C. remove
D. renew