下列选项中，哪项是引起原发性肝癌最常见的病因（）

A.乙型、丙型肝炎病毒感染

B.遗传

C.黄曲霉毒素感染

D.食物中致癌物质

E.寄生虫感染

You are approaching another vessel and see that it has the signal flag “O” hoisted．What is your next action（）.

A.Proceed on present course and speed since the vessel is requesting a pilot

B.Attempt to call the vessel on VHF radiotelephone and begin a search because the vessel has a man overboard

C.Attempt to call the vessel on VHF radiotelephone because it is disabled

D.Approach with caution because the vessel is stopped and making no way through the water