Answer:
c. IRS rules allow the taxpayer to specify which shares being sold
Step-by-step explanation:
As eahc method will make the capital gain or loss to differ the Internal Revenue Service leaves to the stockholder to decide the method
The default method is the FIFO method which states the first shares purchased are the first sale but, leaves choise to the stockhodler to use specific identification which, is what the statement correctly points out.
The method are not "required" but allowed as the stockholder see fit.