It would be "were" and "would." The phrase "if there were" indicates a hypothetical situation....It is not a real.
In this case, the situation presented is very far out. Other examples of this type of phrase would be, "If you were invisible for a day, where would you go?" or "If you were given three wishes, what would you wish for?"
"If...were" could also indicate a probable situation, though...one that is not yet real, but could very well become real. For example, you could say, "If I were a little skinnier, I would fit into this dress." In this case, you could lose the weight and fit into the dress in the near future.
Sometimes "If...were" is used to give advice, too. For example, if a friend tells you that she had a disagreement with her boyfriend, you might say, "If I were you, I would call him and talk to him about it."
Thanks a lot. I know (at least I thought I knew) that subject. But during the exam I thought like that: We don't know if there is life on other planets yet. (We can't say there is not.) It's still possible to discover. And If so, I will go when we find any. In this case, is are-will correct?
I suppose that technically "are...will" would be correct in that case, but it's just not something you would normally hear. It is assumed that discovery of aliens on another planet would be a crazy, far out thing.
My objection to A) is not so much the are/were conditional/subjunctive question, but the use of "will" to talk about visiting other life-sustaining planets.
From what I've read on the subject, a lot of very intelligent people believe space travel outside the solar system is flat-out impossible purely in terms of the energy required to get us there, let alone people alive today with current technology. Certainly you or I are not going to be participating in interstellar travel.
So to me, that is the reason why I would reject A.