thE stonE Chip is thought to BE thE most importAnt tool BECAusE it _______.
A．wAs onE oF thE First tools
B．DEvElopED humAn CApABilitiEs
C．lED to thE invEntion oF mAChinEs
D．wAs CruCiAl to thE DEvElopmEnt oF mAnkinD