Of all the urbanized people of the Americas, the Incas were the most brilliant engineers. The correct option among all the options given in the question is option "b". The most important creation by the Incas was the roadways. Some of the roads had a length of the entire South American Pacific coast. To build cush brilliant roadways in mountainous regions required remarkable engineering skills.
Mostly its everything bit I think the specific one is oil.
This is really really interesting thanks
