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
The reason _______ he was late was _______ he missed the bus.
A.why, because
B.why, that
C.that, why
D.because, why
刮板输送机的()有均载和减缓冲击的作用。
A.链轮
B.液力耦合器
C.牵引链
D.铲煤板