EDuCAtionAl ExpEnsEs ArE tAx-DEDuCtiBlE ______ thE tAxpAyEr CAn show thAt thEsE ExpEnsEs EnhAnCED his or hEr proFEssionAl skills or ExpErtisE.
A．only iF
B．As iF
C．As mAny As
D．As muCh As