read the paragraph. then, add the best topic ...

read the paragraph. then, add the best topic sentence. in 1852, marsh had a hard time climbing mount washington, the tallest peak in the northeast. he wanted to find an easier way to get up the mountain. a train would make it easy, but most trains could not go up a steep mountain. to solve this problem, marsh invented a special train that used wheels with teeth to hang on to the tracks. this system, which was the first of its kind, helped trains climb all the way to the top of mount washington. there are several mountain - climbing railways in the united states. sylvester marsh built the first mountain - climbing railway. special wheels with teeth can help trains climb steep railroad tracks.

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