Answer:
A
Step-by-step explanation:
This is a wonderful question. Usually these things have 4 poor choices and you have to pick the best of the bad.
Not this questions. Except for A, they all answer the question. C and D both speak of our failure at trying to live together. They both speak negatively of our attempt.
B is in the same vein. We failed because our method of resolution was war.
I think the best answer is likely A. Why go to the moon when we had barely found out what was on our own planet. The sentence is about exploration.