与原发性肝癌发病最密切的因素是()。
A.肝硬化
B.病毒性肝炎
C.黄曲霉毒素
D.饮用水污染
E.寄生虫
参考答案:B
A.Bakeries now offer a limited range of albeit excellent products.
B.There are about four kinds of bread, breakfast and dessert pastries.
C.Bakeries sell sandwiches mainly in the working-class areas.
D.France is currently witnessing a boom in sandwich business.
渐开线齿廓的形状与齿轮的()半径大小有关。