Final answer:
The primary difference between stringent and relaxed drainage patterns is the speed of water flow, with stringent patterns found in steep areas for rapid flow, and relaxed patterns in areas with lesser slopes for slower flow. Option A is correct.
Step-by-step explanation:
The primary difference between stringent and relaxed orientation of drainage patterns relates to the speed of water flow. Stringent drainage patterns occur in areas with steep slopes where water flows more rapidly, while relaxed drainage patterns are found in areas with less gradient, resulting in slower water movement.
This distinction in water speed is influenced by various abiotic factors including the slope angle, the shape of the riverbed, and the contributions of tributaries, which affect the width and sedimentation in the river channel as it moves from the source towards its mouth.