Joe and Sue, a married couple, have prepared their own tax returns for several years. Due to lack of tax knowledge, they consult Sam, a tax preparer, for advice on whether any of these returns should be amended. All the following items can be amended except: a) Adding a credit for dependent care that was forgotten on the original return b) Reporting additional interest income that was forgotten on the original return c) Changing the filing status from married filing jointly to married filing separately after the due date of the original return d) Changing the filing status from married filing separately to married filing jointly within the three-year amendment period