The answer is letter a. The Olmec culture is recalled today in part because it was the first Mesoamerican culture to build small cities, most particularly San Lorenzo and La Venta. It was said there were an abundant rainfall and seasonal flooding within the site the Olmec Civilization in those places.
I believe that the answer for this one would be A " endless sky".
Tell me if you got it correct :)
Answer:
That is the ball and socket joint