Read the passage. Then, select the antonym of the word in bold.
Following a catastrophic oil spill in the Gulf of Mexico in 2010, hundreds of dead dolphins washed up on the beaches of Mississippi, Louisiana, and Alabama. A cursory inspection of the devastation convinced many residents that it was caused by the spill, but the National Oceanic and Atmospheric Administration waited for a careful analysis of the dolphins' remains to be carried out before drawing their conclusions. Autopsies finally revealed low adrenal hormone levels, which are associated with oil contamination in mammals.