
The Correct choice is : C. <u>Solids</u>
Sound waves need a medium to propagate, and the most suitable medium for that is solids, where it travel the fastest or with greatest efficiency.
Answer:
True.
In pre-colonial Africa, some primitive versions of government systems were used.
I believe the answer you're looking for is Southwest Asia, looking at a climate map, the drier areas are located to the southwest.
Unitary: no local decisions.
Federal: some local decision.
Confederation: a lot of local decisions.