The answer is A) condition are much harsher on Mars than earth.
I think it was wise because as we know France, U.K. and USA were very strong. But if they were to let other countries join the conference they would start demanding land. Because the U.K. and France promised independece to the Arabs but France and U.K. made a deal behind their back. So if they allowed the Arabs to come they might use that against them and they would get their land. If France and U.K. did that they would power over the coloines they own. They wanted to remain on top so I think it was wise. They would need all that power anyway to defeat the Axis in WW2.
