Critical Reasoning: Conclusion Weakening Questions
Which of the following most logically completes the argument?
A chemical compound has been developed that disrupts the biological messages responsible for the later stages of embryonic development during the reproduction cycles of certain sea creatures. Upon introduction into an area of the ocean, the compound spreads outwards and downwards, reaching an active depth of up to 20 feet. The inventors of the compound are aiming primarily at offering it as a method for controlling the numbers of jellyfish although this will clearly be unsuccessful since __________.
Incorrect.
[[snippet]]This answer choice neither weakens nor strengthens the conclusion and therefore cannot logically complete the argument. The users of the invention and the fact that it will be used tell us nothing of whether or not it will be successful.
Incorrect.
[[snippet]]This answer choice neither weakens nor strengthens the inventors' conclusion and therefore cannot logically complete the argument. The chemical is designed to attack reproduction at a late embryonic stage whereas the planula is a pre-embryonic creature.
Incorrect.
[[snippet]]This answer choice neither strengthens nor weakens the conclusion and, therefore, cannot logically complete the argument. Since the chemical compound effects the later stage of reproduction, details about jellyfish fertilization are irrelevant.
Incorrect.
[[snippet]]This answer choice neither weakens nor strengthens the conclusion and, therefore, cannot logically complete the argument. We already know the chemical spreads down to 20 feet so this physical rule does not help us evaluate its effectiveness.
Superb!
[[snippet]]This answer choice weakens the inventors' conclusion and therefore logically completes the argument. If after fertilization, the reproductive process of jellyfish takes place on the sea floor, then the chemical, which is only active in the top 20 feet of the ocean, will not be capable of affecting the reproduction in any way.
