[求助]GWD-29-37

xyloaries

Rabbitswere introduced to Numa
Island in thenineteenth century.  Overgrazing by theenormous population of rabbits now menaces the island’s agriculture.  The government proposes to reduce thepopulation by using a virus that has caused devastating epidemics in rabbitpopulations elsewhere.  There is,however, a chance that the virus will infect the bilby, an endangered nativemarsupial.  The government’s plan, therefore,may serve the interests of agriculture but will clearly increase the threat tonative wildlife.Which ofthe following, if true, most seriously weakens the argument?
A.   There is less chance that the virus willinfect domestic animals on Numa than that it will infect bilbies.
B.   There are no species of animals on theisland that prey on the rabbits.
C.   Overgrazing by rabbits endangers many of theplants on which bilbies feed.
D.   The virus that the government proposes touse has been successfully used elsewhere to control populations of rabbits.
E.    There is no alternative means of reducing therabbit population that would involve no threat to the bilby.

答案是C，我选的是E。
是否因为C说明，即使不采用该方法，当地物种一样会受到威胁。那么即使采用了该方法，和因为食物减少而受到的威胁相比，因为传染病毒而受到的威胁不一定是增加了。所以是削弱了结论？
那么E呢。是否因为它引申出的结论是“是否要采纳文中的结论”，而不是对文中的结论本身作出评判，所以是错的？
请指教！