Two Scientists Designed a Study to Investigate the Impact of a Recent

Multiple Choice

Two scientists designed a study to investigate the impact of a recent sewage spill in a local river. They compared species diversity in the affected river to species diversity in a nearby river not affected by the spill, and found that the species diversity in the two rivers was roughly the same. The researchers concluded that the sewage spill had little to no effect on the health of the affected river.
Each of the following, if true, would undermine the researchers' conclusion EXCEPT:

A) Prior to the sewage spill, a study had documented greater species diversity in the affected river than was found in this study.
B) The control river experienced a similar sewage spill two years ago.
C) The full damage to an eco-system after a sewage spill can take years, if not decades, to manifest.
D) A sewage spill tends to affect all species equally.
E) The two rivers were remarkably similar in all features and were located in the same geographical area.