How will the right answer fit in terms of support and conclusion?

Only the right answer will be support that must be true if the conclusion is true. It’s typically just as accurate to say only the right answer will be support that doesn’t bring in anything new.

Highlight the main conclusion in the passage, if there is one:

it will not be economically feasible to colonize Mars.

[SUPPORT]. But because [SUPPORT], [CONCLUSION].

You want to recognize how matter-of-fact the author is about the conclusion. No exceptions or wiggle room, not even “it might not be”. That means they’re claiming this is a necessary condition. In other words, they’re implying a rule: if the costs of transporting materials are so high, that guarantees a colony on Mars will not be economically feasible. The right answer will support that there’s no other way to make a colony on Mars work.

Map the wording of the answers to the wording of the passage:

(A) …will human habitation be established on Mars.

Be careful, this is changing the wording in a way the author didn’t imply. Just because it won’t be “economically feasible” doesn’t necessarily mean human habitation won’t be established.

(B) …is not expected to decrease in the near future.

Don’t fight the passage. We’ve been told the costs would be “so high”, and you’re expected to accept that as a fact. Even if the costs go down, how do you know they’d go past the critical point of being affordable? You don’t have any info about that, so no way this is “required by the argument”.

(C) Earth is the only source…

This is really specific. The “source” of the materials is never mentioned, only the destination. So the conclusion could still work regardless of where the materials are being brought from.

(D) No significant benefit would result…

There’s nothing about the “benefit” in the passage, only the “costs”. This is definitely bringing in something new.

(E) Mars is not a practical source of the basic materials…

I could see you thinking that the “source” is irrelevant, but the passage absolutely implies that Mars is not the source. Right? Why would we have to transport materials “through space” if they’re already on Mars? This answer supports that if transportation costs are too high, then a colony is not feasible, because there’s no other way to do it.

(E) is the correct answer.