Answer:
Option D, gravel-sized particles
Step-by-step explanation:
In a stream which is moving at a very fast rate carries the fine sand and dissolved particles with the flow. The turbulence of the stream does not allow light weight particles to settle down. While gravel being heavier than all the debris (carried by flowing water) tries to settle down under the action of gravity. Thus out of all the particles gravel will settle first.
Hence, option D is correct