They give us more information about what they learned.
Whoch birds are migrating is my answer because, for a the birds are migrating because its winter for c birds are already going since one of the questions are where the birds are going, and d is that they are going there to not freeze, the only logical choice FOR ME is B
The correct answer is - C. The river carried enormous amounts of silt.
The Yellow River, got this nickname because it is yellowish from the enormous amounts of silt it carries. When there were heavy rains, or the snow was melting, the river got more water, but also more silt, so the silt was partially blocking the free movement of all of the water, so it was flooding the surrounding are. In one way, the floods were terrible because they were destroying pretty much everything on their way, but on the other side, were living huge amounts of deposits that were fertilizing the soil for the agriculture.
The Mediterranean sea and the surrounding area
there are more than 200 countries in the world
