布—查氏综合征患者合并门脉血栓的比例是()

A．<5%

B．约20%

C．约50%

D．>90%

E．约10%

How does an icebreaker normally free a ship which has become beset while navigating independently?（）

A.By backing down the track and cutting out ice on either bow

B.By approaching from the stern and crossing ahead at an angle of 20° to 30° to the beset ship's course

C.By overtaking the beset ship，running ahead and then backing down the track to the beset vessel

D.By approaching the vessel from astern and towing the beset vessel stern first