Self-study
When so many oysters died off the coast of Britain that some native species were threatened with extinction, the fact that the water temperature had recently risen was at first thought to be the cause. ██████ ████████ ███ █████ ███ ██████████ ██ ██ ███ ████████ ████████ ███ ██████ ████ ██ ████ █████████ ███ ███ █████ ██ ██████ ███████████ ████ ██████ ███ ███ ██████ ██████████ ████ ████████ ████ ███████ ███████ ███ ███ ███████████ ██ ███ ██████████ ██████ ███████ ████ ███ ██████
"Surprising" Phenomenon
Despite the ban on TBT, which had caused a decline in the native oyster population, the now-endangered oysters haven’t recovered.
Objective
The correct answer will be a hypothesis that explains why the TBT ban didn’t help the endangered oyster population as expected. That explanation must provide some new problem facing the oyster population after TBT was banned, or some reason that TBT was in some way useful to the oyster population. The result must be that the oyster population didn’t rebound.
13.
Which one of the following, ██ █████ ████ █████ ██ ███████ ███ ███████ ██ ███ ██████ ██████ ███████████ ██ ████████
a
The increase in █████ ███████████ ███ ██████ ██ ███ █████ █████ ███ ███████████ ███ ███████
The increase in water temperature wasn’t the problem. We need to know why the TBT ban didn’t help the osyters, and without more information about the effects of the water temperature, this isn't helpful.
b
Native oysters rely ██ █████████ ███████ ██ ████ ████ ██ ███ █████████ ████ ████ ██ ███ █████ ██ ██████
If anything, this eliminates one way the TBT ban could’ve gone wrong: that barnacles competed with oysters for food. It certainly doesn’t explain why the TBT ban was ineffective.
c
TBT also killed ████████ █████████ ██ ███████ ████ ████████ ██ ███ ███████ ██ ██████ ███████ ███ ████ ███ ██████ ███ ███████
So TBT eliminated competition that harmed the native oysters. The competition intensified after the TBT ban, hence why the native oyster population didn’t rebound.
d
Other chemicals that ███ ████ ██ ██████ █████████ ████ ███ █████ ██ █████ ████ ██ ████ ██████ ██████ ██ ███ ██████ ████████████
Like (B), this removes a possible downside of the TBT ban: that the chemicals that replaced TBT were also harmful to the oysters. This doesn't explain why the oyster population didn’t grow after the TBT ban.
e
TBT is more ██████ ██ ███████ ██ ██████ ██████ ████ ██ ██████ ███████
But TBT was banned, so it can’t factor into an explanation for why the oyster population didn’t rebound. This doesn't tell us what other factor is keeping native oyster populations low.