8. _______they to cut down the cost of advertising, the cost of production_______significantly fall.
Are; will
Were; shall
Are; should
Were; would
本题主要考查虚拟语气的倒装现象。
由选项可知，题干意为“ 如果他们真的削减广告成本，那么生产成本将大幅下降”。首先，由前半句中的they to cut down可推测出，本句使用了if they were to…thecost would…结构来表达对将来情形的预测。其次，因为前面条件句中省略了if, 所以产生了倒装现象，需将be动词提前。因此，D项符合题意，A、B、C三项均不符合。故正确答案为D。