In the lion the witch and the wardrobe why did the pevensie siblings save Narnia

So the White Witch didn't make it so that it was winter all year round

Explanation:Most of the novel is set in Narnia, a land of talking animals and mythical creatures that is ruled by the evil White Witch. In the frame story, four English children are relocated to a large, old country house following a wartime evacuation. The youngest, Lucy, visits Narnia three times via the magic of a wardrobe in a spare room. Lucy's three siblings are with her on her third visit to Narnia. In Narnia, the siblings seem fit to fulfill an old prophecy and find themselves adventuring to save Narnia and their own lives. The lion Aslan gives his life to save one of the children; he later rises from the dead, vanquishes the White Witch, and crowns the children Kings and Queens of Narnia.

the answern should be b, if it is the part where the mob has gathered

what is the question ?