What is the most important achievement of Inca people?  
Development of complex government system

 
Development of herbal medicines

 
Development of astronomy

 
Development of road network

This is technically an opinion, but overall the answer should be

C. Development of astronomy

Explanation:

I would say C because B and D were nice, but didn't last past the fall of the Incas. Then you have A, again this was very good, and it might have influenced a few other civilization past the Incas, but overall, almost every country nowadays have a unique form of government. The answer is C because we still use most things that the Incas learnt about astronomy to this day all around the world.

May I have brainliest please? :)

the correct answer is c.