A significant number of farmed rainbow trout at a series of connected river hatcheries have died over the past month. Necropsies revealed both an unidentified parasite and elevated levels of a known toxic algae compound in the fishes' tissue. Water samples taken downstream from the hatcheries confirmed unusually high concentrations of the toxin-producing algae. Therefore, although both the parasite and the algal toxin are capable of killing trout, the algal toxin is the more probable cause of these particular deaths.

Which of the following, if true, provides the most additional support for the conclusion above?

(A) Parasitic infections are considerably harder to detect through standard necropsy than algal toxins are.
(B) Rainbow trout are the only fish species currently being farmed at these particular hatcheries.
(C) The toxin-producing algae is present in low concentrations in this river system during most months of the year.
[D] Nearly all of the trout that died were mature adults, even though juvenile trout are known to be far more vulnerable to this particular parasite than adults are.
(E) Several seasons ago, a comparable die-off at a different hatchery downstream was later traced to an unrelated bacterial infection.