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

关于氟斑牙的临床表现叙述错误的是（）

A.釉面变得没有光泽

B.釉面出现缺损

C.釉面变成黄色，有斑点

D.氟斑牙不影响正常的饮食

E.严重的牙齿不同程度出现损伤