The topic of the paragraph is the information that the farm and the children were alone in the world.
We can arrive at this answer because:
The topic of a paragraph is the subject that the paragraph is addressing.In this paragraph, the main issue is that the parents of the children, who owned the farm, had died.This death left children and farms abandoned.The fact that the farm hasn't had anyone to take care of it for years is a reflection of the children's situation.The topic of a paragraph should be something objective and direct, allowing the reader to understand without difficulties.
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