GMAT Critical Reasoning (CR) | Deep tillage is even more deliterious to the world's topsoil

My 2 cents

-- Conclusion is stated by the author..... "Farmers must strive to incorporate No-till methods"
a) Negated - "Topsoil erosion does make farmers want to till more deeply"....so what ? Still the conclusion stated by author is not weakened that "Farmers must strive to incorporate No-till methods", The conclusion stated by author still holds good that topsoil erosion is bad and farmers must use no till methods
b) Its already stated in the passage
c) correct
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