— Has your brother returned from the USA yet? 

— Yes, but he ____ here for only two days before his company sent him to Australia. [ ]

A. stayed

B. has stayed

C. will stay

D. was staying

为了与供应商建立互惠关系，稳定供需关系，在采购中可根据环境变化，对采购规格、数量及价格做灵活的调整，这种采购方式是（）。

A.招标采购

B.订价采购

C.询价采购

D.议价采购