材料：

The 4，426gt Swedish vessel Skagern sailed for her next port，Strood，with a draught of 5.95m．The master soon realized，however，that he would not make the tide for berthing if he proceeded to the Medway as planned，to pick up the pilot at the North East Spit．He therefore decided to change the passage plan by shortening the distance and embarking his pilot at the Sunk light vessel．The officer on watch，2/O，was told to make the necessary adjustments and lay off the new courses．

The 2/O made the original plan based on waypoints calculated and entered by another officer．These had been marked on the various charts and had already been entered into the GPS navigator．When he amended the passage plan he used the GPS to calculate a new course from a waypoint off Lowestoft direct to the Sunk pilot station．In doing so，he didn&39;t realize he had missed out a pre-programmed waypoint in the GPS for a position to the east of the East Shipwash buoy．He didn&39;t notice that his course line intersected the 5m depth contour to the west of the East Shipwash buoy．

The master did not check the amended passage plan and Skagern continued with her passage．2/O came on watch again four hours before the vessel was due to arrive at the pilot station．One hour before arrival at the Sunk 2/O prepared to embark the pilot．

He saw the North Shipwash buoy and passed about three cables to the east of it．Shortly afterwards he saw two more buoys ahead of him，the East Shipwash on his port bow and the North-West Shipwash on his starboard.It did not occur to him that anything might be wrong．Shortly afterwards，Skagern ran aground at a full speed of 14 knots．He had found the Shipwash Bank．

Although two tugs were dispatched from Harwich to standby，the master was able to de-ballast his vessel and refloat her successfully with the aid of the main engine．There was no pollution and there appeared to be no damage．

问题：

To embark the pilot earlier Skagern ________．

A.speeded up

B.shortened the distance by adjusting the planned passage

C.made the tide

D.engaged trade every two weeks

The grounding was caused by the reason of ________．A.the second officer missed a waypoint when steaming to the pilot station

B.the depth around the pilot station is 5.95m which is not sufficient to allow the vessel to keep always afloat

C.the GPS had something wrong when calculating the course

D.the vessel did not make the tide due to her late arrival

The vessel was refloated ________．A.with the aid of reverting her main engine and pressing up slack ballast tanks

B.herself by pumping out some of her ballast and the aid of her main engine

C.with the aid of her main engine and the two tugs from Harwich

D.with the aid of tide and tugs

The lessen of this accident is that ________．A.without proper planning of the ballasting and de-ballasting programme the vessel is likely to be involved in such accident as grounding

B.a vessel should be well prepared for grounding when proceeding toward pilot station

C.when grounded，a vessel should try to contact the nearest coast station to apply for the aid of tugs

D.in this age of the GPS and push-button navigation，it is all too easy to be lulled into a false sense of security and assume the position indicated is correct

请帮忙给出每个问题的正确答案和分析，谢谢！