The technique that this sentence best illustrates is understatement.
Understatement means that you are not showing the full 'strength' of something, but it is rather understated - so here, the coach only said that 'he was glad' even though his team won the Super Bowl, which is a huge deal. So his emotions should have been way stronger.
With the A. migration of people from fertile areas, knowledge of agriculture spread by diffusion.
When people migrate from a place, they move into other areas. When something diffuses, it spreads around.
<h2>there is no why, only try</h2>
