The testing period for determining whether a $5382$ corporate stock ownerahip change has occurred is defined as which of the following periods?

a$.$ The three$-$year period ending on$,$ but including, the date of the change in ewnembip.

b$.$ The there$-$year period ending en$,$ but excluding, the dane of the change in evenahie.

c$.$ The five$-$year period ending on$,$ but including, the date of the change in ownenhip.

d$.$ The five$-$year period ending en$,$ but excluding, the date of the change in ownenlip.