In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Q: 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.
Links: a. Cascade Range b. Skykomish River c. Washington State Route 9 d. Cascade Range
A:
a