Well not much to go off by but a predicate is part of a sentence or clause containing a verb and stating something about the subject
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This question is a "what sounds the best and is the most logical?" I would pick this one.
The Columbia River, which forms most of the border between Oregon and Washington, flows into the Pacific Ocean.
The clause beginning with <em>which</em> is an adjective clause that describes the Columbia River more extensively. The others are either in the wrong order C or they are not adjective clauses like D
Just to go with the flow basically life changes