Question ID:PT86 S1 Q13 Passage: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.  Later, however, the cause was determined to be the chemical tributyl tin (TBT), used to keep barnacles off the hulls of boats.  Legislation that banned TBT has nearly eliminated that chemical from British waters, yet the populations of the endangered oyster species have not grown. Stem:Which one of the following, if true, most helps to explain the failure of the native oyster populations to recover? Correct Answer Choice:CChoice A:The increase in water temperature has slowed in the years since the legislation was passed. Choice B:Native oysters rely on different sources of food than do the barnacles that live on the hulls of boats. Choice C:TBT also killed imported varieties of oysters that flourish at the expense of native oysters now that the waters are warmer. Choice D:Other chemicals that are used to remove barnacles from the hulls of boats seem to have little effect on the oyster populations. Choice E:TBT is more deadly to oysters in colder waters than in warmer waters.