ACCorDing to thE pAssAgE, moDErn soCiEtiEs Control supply AnD DEmAnD ______.
A．By Fixing priCEs in spECiFiC inDustriEs
B．By mEAns oF monEy AnD thE priCE mEChAnism
C．By kEEping A wAtChFul EyE on rElAtivE priCE ChAngEs
D．By DirECt intErvEntion in thE priCing oF gooDs AnD sErviCEs