Cora’s motivations advance the plot primarily through her desire to get her brother back, which leads to actions that resolve the plot. This is reflected in her protective nature towards Ruky and the need to ensure his safety and well-being, especially given their circumstances as orphans living alone. Her actions driven by this desire ultimately drive the story forward, leading to key developments and resolutions in the narrative. Therefore, the correct response is:
Her desire to get her brother back leads to actions that resolve the plot.