Question Explanation
The question asks what can be inferred from the passage, which indicates that this an inference question. Do not bother breaking the passage into its conclusion, premise, and assumption for inference questions. Instead, focus on what the passage states directly. The correct answer must be true based on the facts in the passage. The passage states that advertisements…claim that continually washing one's hair with the same brand of shampoo eventually reduces the shampoo's effectiveness, because all shampoos have residues which build up over time. Evaluate the answer choices and, based upon the information in the passage, select the answer that represents the consumer response advertisers seek.
Choice A: No. A product which can remove the residue left by any shampoo is out of scope. The advertisements state that continually washing one's hair with the same brand of shampoo can be problematic because all shampoos have residues which build up over time, but the passage does not address any other product than shampoo.
Choice B: No. The phrase switch to the advertised brand is a reversal. The advertisements state that continually washing one's hair with the same brand of shampoo can be problematic because all shampoos have residues which build up over time. Thus, even the advertised shampoo will become less effective if used continuously.
Choice C: Correct. The advertisements state that continually washing one's hair with the same brand of shampoo eventually reduces the shampoo’s effectiveness. Therefore, it can be inferred that consumers should periodically change their shampoo. The advertisers hope that customers will periodically use the advertised brand without switching to it permanently.
Choice D: No. Never is extreme language, which should raise suspicion. The passage does indicate that all shampoos have residues which build up over time, but it does not specify whether a week is enough time for the residue from a shampoo to accumulate in the hair. Therefore, the idea that one should [n]ever use the same brand of shampoo for more than a week is too extreme.
Choice E: No. Residues that protect hair are out of scope. The passage states that all shampoos have residues which build up over time, but does not state that the residues from the advertised brand are in any way different from those of other shampoos.
The correct answer is choice C.