Not until all the fish died in the river______how serious the pollution was.
【正确答案】 A
【答案解析】当never,hardly,seldom,scarcely,little,not only,by no means等表示否定或部分否定意义的词或短语位于句首时,句子应部分倒装,即将助动词、情态动词、系动词等提至主语前面。故选A。