Evidence suggests that the ancient Olmec used obsidian to make blades and other tools; however, obsidian is not a naturally occurring raw material in the area that the Olmec inhabited. According to this information, which of the following was probably true about the Olmec?
A.
The Olmec reused pieces of obsidian left over from another civilization.
B.
The Olmec were conquered by another civilization in Mesoamerica.
C.
The Olmec used surface deposits of obsidian that left no trace of their existence.
D.
The Olmec had access to and controlled a large trading network.