A

Recurrent streptococcal tonsillitis that has already produced systemic sequelae such as rheumatic fever or post-streptococcal glomerulonephritis is a classic (though now uncommon) indication for removing the tonsils, because eliminating the pharyngeal focus prevents further immune-mediated damage [Gastpar, 1984, PMID 6727503]. Simple “colds” (recurrent nonspecific upper-respiratory infections) are specifically excluded as a reason for surgery, and modern guidelines no longer recommend tonsillectomy merely to clear a diphtheria carrier state [Hoddeson, 2009, PMID 19130955]. Thus only choices a and b are true indications.