Which of the following is generally correct regarding regrouping under Code Sec. 469:
a. after a taxpayer has grouped activities, the taxpayer may only regroup those activities in the next taxable year
b. after a taxpayer has grouped activities, the taxpayer may only regroup those activities within the next two taxable years
c. after a taxpayer has grouped activities, the taxpayer may only regroup those activities within the next three taxable years
d. after a taxpayer has grouped activities, the taxpayer may not regroup those activities in subsequent taxable years