下列哪项不是MRI检查禁忌证（）。

A.有心脏起搏器

B.幽闭恐怖症患者

C.有心肺监护仪者

D.有碘过敏史

E.术后动脉夹存留者

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