PrepTest 31, Section 2, Question 2
For the last three years, entomologists have been searching for a parasite to help control a whitefly that has recently become a serious crop pest. Believing this new pest to be a variety of sweet-potato whitefly, the entomologists confined their search to parasites of the sweet-potato whitefly. Genetic research now shows the new pest to be a distinct species, the silverleaf whitefly. Therefore, the search for a parasite has so far been wasted effort.
For the last three years, entomologists have been searching for a parasite to help control a whitefly that has recently become a serious crop pest. Believing this new pest to be a variety of sweet-potato whitefly, the entomologists confined their search to parasites of the sweet-potato whitefly. Genetic research now shows the new pest to be a distinct species, the silverleaf whitefly. Therefore, the search for a parasite has so far been wasted effort.
For the last three years, entomologists have been searching for a parasite to help control a whitefly that has recently become a serious crop pest. Believing this new pest to be a variety of sweet-potato whitefly, the entomologists confined their search to parasites of the sweet-potato whitefly. Genetic research now shows the new pest to be a distinct species, the silverleaf whitefly. Therefore, the search for a parasite has so far been wasted effort.
For the last three years, entomologists have been searching for a parasite to help control a whitefly that has recently become a serious crop pest. Believing this new pest to be a variety of sweet-potato whitefly, the entomologists confined their search to parasites of the sweet-potato whitefly. Genetic research now shows the new pest to be a distinct species, the silverleaf whitefly. Therefore, the search for a parasite has so far been wasted effort.
Which one of the following is an assumption on which the argument relies?
All varieties of the sweet-potato whitefly are serious crop pests.
If a crop pest has a parasite, that parasite can always be used to control that pest.
The chances of successfully identifying a useful parasite of the new pest have increased since the proper identification of the pest.
No parasite of the sweet-potato whitefly is also a parasite of the silverleaf whitefly.
In the last three years, the entomologists found no parasites of the sweet-potato whitefly.
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