The sentence that best supports the answer in part A, which likely emphasizes the commitment to peace and the need for cooperation among nations, is:
B. "...that both sides begin anew the quest for peace, before the dark powers of destruction unleashed by science engulf all humanity in planned or accidental self–destruction."
This sentence highlights the urgency of seeking peace and the risks posed by scientific advancements, aligning with the themes of cooperation and the pursuit of stability.