多选题 A certain additive put in gasoline to reduce air pollution is actually ______ groundwater, a finding that shows that even the most well-intentioned fixes can sometimes ______.

A、 contaminating
B、 purifying
C、 saturating
D、 prevail
E、 backfire
F、 reciprocate

【正确答案】 A、E

【答案解析】[解析] ●actually说明前后反义重复。
●第一空与reduce air pollution(减少空气污染)反义重复。contaminate污染，purify净化，saturate浸润。答案选A。
●prevail奏效，backfire适得其反，reciprocate往复运动。答案选E。