Thanks understood where i went wrong. Also really like the new update
This is a pretty annoying question. I don't like E or B personally.
B talks about the Scottish seals, telling us that they died because of a certain virus. This requires us to assume that the same strain of virus killed both populations and I think that's too much of an assumption on the GMAT.
E talks about all marine mammals but at least in the Baltic sea and the same year, so this is promising but good news ends here. This answer choice requires us to assume that the other marine mammals picked pollution from the Baltic Sea, and only with that assumption we can make the conclusion that higher pollution levels cause the other mammals to also die, thus Seals are not alone in this virus infested polluted sea and therefore that supports the argument.
So I would pick E over B but I don't like either.
A) is irrelevant
C) is incomplete and irrelevant. We do not know which seals it is talking about - all, dead, or alive
D) Weakens the argument