Many homeowners regularly add commercial fertilizers to their lawns and gardens to maintain a healthy balance of nutr...

shunhe on October 2, 2020

Hi @ritagentile,

Thanks for the question! Let’s take a look at what the stimulus is telling us. We’re told that homeowners regularly add commercial fertilizers so their lawns have a healthy balance of nutrients. The widely available fertilizers only have macronutrients, but to be healthy in the long-term lawns need macronutrients and micronutrients. Micronutrients are depleted when grass clippings are raked up and not allowed to decay and return to the soil.

Now we need something that can be properly inferred from the statements above. So this is a must be true question. (D) tells us that for soil to remain healthy in the long term, it requires the regular addition of both commercial fertilizers and a source of micronutrients such as grass clippings that are allowed to decay and return to the soil. This is a pretty tempting answer choice, but there is a problem with it. Do we know that commercial fertilizers are REQUIRED? No, we only know that macronutrients are required. And macronutrients can come from other sources! The argument doesn’t preclude us having some long term healthy soil with some other source of macronutrients (and micronutrients). And that’s why we can’t properly infer (D) from the passage.

Hope this helps! Feel free to ask any other questions that you might have.