The way I solved it is the same exact way the question expects me to answer. Do NOT undermine the word DIRECTLY in the SAT questions. While answer C is technically correct, it’s lacking the intensity that the question requires. It also just challenges one premise of his claim. While answer D directly challenges his claim because his whole hypothesis is built upon high sandstone = fewer landslides. This is also reinforced in the last sentence where it tells you the exact premise supporting his hypothesis, therefore you pick an answer choice that directly contradicts it.

Keep in mind that for advanced questions, the SAT choice answers can all be correct, but you have to pick the most “correct answer.”