Answer:
Vatican City (I know it has city in the name lol)
Explanation
Trust me on this one though haha
The land mass is technically a country because of the Lateran treaty of 1929, which made Vatican city an independent state under the Holy See.
Temperature and density increases from the crust to the core.
Levees and embankments allow humans to c)settle below river level. A levee is defined as "an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels." This definition can also be used for the term embankment.
There is a grand total of 196 countries in the world. Hope this helped.
I would say C. because a lot of people settled there.