Correct answer: A. Arab-Israeli
Details/context:
Jewish immigration into the Palestine region had been happening since the end of the 19th century and escalated in the early 20th century. The pressure for Jews to leave Europe escalated when the Nazis came to power in Germany. The world became more sympathetic to the plight of the Jews after the horrors of the Holocaust became known.
After World War II ended, the United Nations (UN) adopted a plan for the partition of Palestine that would create a portion of that territory as the state of Israel. Arabs in the region and surrounding Arab nations were not in favor of this. On May 14, 1948, the Jewish leaders in the land proclaimed their independence as a nation, and a war with Arab peoples and nations in the region followed. Israel won that war and established itself as a nation. The new state of Israel was granted membership in the UN in 1949. So this was an Arab vs. Israeli conflict.
Muslim-Jewish conflict is incorrect because not all Arabs in the region, opposing the formation of Israel, were Muslim. A sizable percentage then of Arabs in the region were Christian. The percentage of Christians among Palestinians and surrounding Arab nations today is less than it was in the 1940s, but there are still many groups of Christians there. And though religion has factored into the conflict, it's not all about religion. Many of the founders of Israel were not particularly religious, though they were of Jewish ethnicity.