During the past 120 years, the world three waves of global economic integration（联合）.
A. witnessed
B. witnesses
C. has witnessed
D. will witness
网友回答
A. witnessed
B. witnesses
(答案→)C. has witnessed
D. will witness
解析：考察时态。本题的关键在于during the past 120 years是与现在完成时连用，句意：在过去的120年里，这个世界已经经历了全球经济联合的三次浪潮。故C正确。