A               

题目分析：考查强调句。句意：直到1970年，经过七年战火，战争才最终结束 。come to an end 终结。Not until引导的倒装 句与强调句连用，原句为 not until 1970 did the war finally come to an end after  seven years of hard fighting.故选A项。          

考点 : 考查强调句