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A - ... that the Yankee peddler has learned before him... Here the "has learned" is present perfect. This action took place is the past and has completed so we cannot use the present perfect "has learned"
B- for the same reason as A -- has learned is incorrect
C - distorts the meaning, i think the intend was to suggest that it was lincoln who discovered the secret in his young manhood and not the yankee peddler
D- This clearly states that lincoln learned the secret in his young manhood and the lists the secret with ":" - the secret being how to use a good story to generate good will.
E- I think, it should have been "discovering" instead of "discovered" ... don't quite know the grammatical reason behind this.
Feel free to correct me if the explanations are inaccurate.