新老矛盾交织，周期性、结构性问题叠加，经济运行稳中有变、变中有忧。

（译：An interlacing of old and new issues and a combination of cyclical and structural problems brought changes in what was a generally stable economic performance , some of which caused concern.）

问：An interlacing 和 a combination中的a为什么不用the ?

"changes in what was a generally"中，为什么又多用了what was，去掉不可以吗？