Robot satellites relay important communications and identify weather

Remember, we are not asked to pick an answer choice that PROVES that the argument is invalid. Instead, we simply need the answer choice that "most seriously" weakens the argument. With that in mind, bb is spot on... none of the other four options would seriously weaken the author's argument, so we are left with (E) by default.


Also, choice (E) says that repairing robot satellites is "more costly and less practical" than sending new, improved satellites into orbit. The replacements are, themselves, satellites, so it would make sense that choice (E) also applies to the replacement satellites.

Do we know for sure that this is the case? No. Maybe for some reason it will become cheaper and more practical to repair the new ones instead of replacing them. But that possibility doesn't really change anything: the argument says that we will NEED astronauts to make satellite repairs. Choice (E) says, "Well, no, we can just replace the satellites instead of doing repairs."

Sure, you can counter choice (E) with the possibility described by AdityaHongunti, but all that does is slightly weaken the weakener! Even if that possibility exists, choice (E) tells us that the logic of the argument is flawed. Just because "the satellites can be repaired only in orbit" does NOT mean "that space flights carrying astronauts must continue."

By simply describing why space flights carrying astronauts might not actually be needed, choice (E) seriously weakens the argument.

I hope this helps!