Think about, maybe it is (D) They focused only on solving the problems & issues that had troubled their cities in the past. you see they would be focusing their city a lot because they don't what can destroy their and what can't. they have to make sure that their is no bad guys attacking their fort and that there is no problems with the way the cities were built.
hope i helped
Add something gor we can answer is clearier
Answer:
It can be paragraph 6,maybe
To make there point more clearer and not always have to go into detail so they might leave a couple of things out.