求助！语文分册48题

泡沫HX

Reporting that one of its many problems had been the recent extended sales slump in women's apparel, the seven-store retailer said it would start a three-month liquidation sale in all of its stores.
A its many problems had been the recent
B its many problems has been the recently
C its many probems is the recently
D their many problems is the recent
E their many problems had been the recent

正确答案是A

问题：如何判断时态应用过去完成时？
求解答~~

kiwifoodtown

动作在said之前发生，用过去完成时态。