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In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.

Question: How tall is the mountain range where the Snoqualmie and Skykomish Rivers originate? Passage:The Snohomish River forms at the confluence of the Snoqualmie and Skykomish Rivers just west of Monroe. Both of these rivers originate in the Cascades and drain the west slopes of the mountains in southeastern Snohomish County and northeastern King County. The Snohomish River flows generally northwestward from the confluence, passing under state route 522 and flowing alongside Lord Hill Park before reaching downtown Snohomish. Here, it is joined by the Pilchuck River, its main tributary, and flows under state route 9. From Snohomish, the river continues northwestward through a broad floodplain, forming the eastern boundary of the city of Everett. The final few miles of the river in Everett form the Snohomish River estuary, a river delta that features wetlands and tideflats spread out across various islands and arms of the river. Several bridges carry U.S. 2, Interstate 5, and state route 529 across the delta. The river then empties into Possession Sound, which is part of Puget Sound, between Everett and Marysville.

Output:
The Snohomish River forms at the confluence of the Snoqualmie and Skykomish Rivers just west of Monroe