Final answer:
Esther and Chaya joined the ZOB (Jewish Fighting Organization), which was significant in the Warsaw Ghetto Uprising of 1943. The correct option is A.
Step-by-step explanation:
In the book Resistance, Esther and Chaya joined the united group in Warsaw known as the ZOB (Jewish Fighting Organization). The ZOB was a Jewish resistance group that played a pivotal role in the Warsaw Ghetto Uprising in 1943.
This uprising was a direct response to the Nazis' efforts to transport the remaining ghetto population to concentration camps. Despite facing overwhelming odds, the ZOB members constructed bunkers, collected weapons, and prepared to fight.
Their resistance was ultimately quelled, but their bravery remains a significant symbol of Jewish resistance during the Holocaust.