Since there is no survival value in an animal's having an organ that is able to function when all its other organs ha...

Jacob-R on November 24, 2018

I’m happy to help. One technique that I find useful when the question stem asks you to find the “main point” of an argument is to think specifically about how any given sentence in the passage relates to every other sentence. That is, does one sentence serve as a premise to the next? Is a sentence providing evidence that supports a sentence that is a conclusion? Or does the sum of two sentences give us an overall conclusion?

That third option is what is happening in this question. You mentioned that you thought the first sentence was the main point: that it is probably within the reach of human technology to make the climate of Mars inhabitable. But think about that sentence as it relates to the next two. We learn from sentence two that it might be several centuries, but that that has happened in human history before. Seems like support for sentence one — and we still don’t know if sentence one is a premise or a main point yet.

But when we move on to sentence three, we learn that research efforts are justified if there is even a chance of making another planet inhabitable. How does that relate to sentence one? It gives us some totally new information, namely that research efforts are justified if there is a chance of making another planet inhabitable. And we knew from sentence one that Mars can be made inhabitable. And therefore, we can glean the main point: that research efforts aimed at Mars are justified.

I hope that helps! Please let us know if you have further questions.