The correct option is (c) Boulder River Stage
Easiest explanation: The river bed in these reaches is created by itself, consists a mixture of boulders, gravels, shingles, and alluvial sand deposits. In latter stage, the river flows through deep well defined beds and wider floodplains. Here the river flows in a straight course. Due to the floods, the boulders and material travels downward and gets deposited there after floods. Because of the opposition to the flow due to these obstructions the river takes new course and thus widens the river bed.