Answer:
C:It weakens the argument because it shows that the outhor may have failed to consider all outcomes.
Explanation:
According to the given excerpt, it is narrated that some certain methods have to be adopted by other schools which is a sure fire way to improve the output of students. This is based on a faulty premise that because it worked for one school, it would work for other schools.
Hence, the effect the use of the logical fallacy in this paragraph have on the credibility of the author's argument is that it weakens the argument because it shows that the author may have failed to consider all outcomes.