The doctor says that mother won ' t be able to walk until the bones of her leg have knitted together 医生说母亲只有等她的腿骨长合在一起了方可走动。
2.
From the picture we know the beijing - jinan railway is the sum of two parts : the beijing - tianjin railway and the tianjin - jinan railway 生：从图上可以看出，北京到济南的铁路长，就是把北京到天津的铁路长和天津到济南的铁路长合起来，所以要用加法。
