______ the costs and efforts spent on market research are great,

______ the costs and efforts spent on market research are great, the exporter must quickly ______ the markets that will not repay the research efforts and narrow ______ the scope of his research.
A、Since, eliminate. down
B、While,destroy, up
C、Although,cancel,out
D、When,in, prohibit
【正确答案】：A
【题目解析】：句意：由于花在市场研究上的成本和精力是巨大的，出口商必须迅速消除那些无法回报其研究努力的市场，并缩小他的研究范围。