177. 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. liquefying, founder
B. contaminating, backfire
C. purifying, boomerang
D. saturating, reciprocate
E. polluting, prevail
178. The biologist's description of the wolf pack was trully ______ , devoid of any emotion or personal prejudice.
A. dispassionate
B. insubstantial
C. esoteric
D. capricious
E. indignant