题目内容：

It's only 40 minute's walk from the center of BeiJing by groundfloor,对划线部分提问
only 40 minute's walk画线

优质解答

only 40 minute's walk 说的是路途远近（只需步行……分钟）,因此对路途远近提问,用how far,这个问句可以是这样：
How far is it from the center of Beijing.