why shoulD Anti-virus soFtwArE BE upDAtED At lEAst onCE A wEEk
A．BECAusE thE nEwly puBlishED Anti-virus soFtwArE is morE ExpEnsivE.
B．BECAusE thE prEvious(先前的) Anti-virus soFtwArE CAnnot work Any longEr.
C．BECAusE thE invEntors oF virusEs hAvE suggEstED this iDEA.
D．BECAusE ComputEr virusEs ArE AlwAys DEvEloping.