Answer:
d. the Flynn effect.
Explanation:
Based on the information provided within the question it can be said that this fear has been most directly alleviated by the discovery of the flynn effect. This refers to the observed and documented increase in test scores over the years. It was a study undergone and documented by James Flynn in 1984. This alleviates this fear as it shows proof that test scores have not declined but instead increased regardless of the higher birth rates.
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