Is it the last sentence in the question a principle or subsidiary conclusion? Is there any other strategies I can implement towards argument structure/logical reasoning that are different from the video??

I put C as the correct answer choice because i knew that the argument revolves around the fact that homelessness is a serious problem (conclusion) and the example with the real estate and how there is no lack of housing units available to rent through the newspaper is the premise. From there I realized that one can accept or deny the conclusion. But I kindly want some clarification for the last sentence if it's a premise, principle or subsidiary conclusion. Thanks