问题补充：
The past two years a sharp rise in oil price，which adds to the burden of auto transportation industry.
A. witnessed
B. witnesses
C. is witnessing
D. has witnessed
答案：
A. witnessed
B. witnesses
C. is witnessing
(答案→)D. has witnessed
解析：考查时态：句意：在过去的两年里我们目睹了油价的急剧上升，这增加了汽车运输业的负担。the past two years 是表示过去的两年中，是现在完成时的时间，此处是过去两年油价的上升对现在造成影响，故用现在完成时。选D，
